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sourcemod/extensions/sqlite/sqlite-source/btree.c
Scott Ehlert 251cced1f8 Spring Cleaning, Part Ichi (1) 
Various minor things done to project files
Updated sample extension project file and updated makefile to the new unified version (more changes likely on the way)
Updated regex project file and makefile

--HG--
extra : convert_revision : svn%3A39bc706e-5318-0410-9160-8a85361fbb7c/trunk%401971
2008-03-30 07:00:22 +00:00

6891 lines
212 KiB
C
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/*
** 2004 April 6
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id$
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"
/*
** The header string that appears at the beginning of every
** SQLite database.
*/
static const char zMagicHeader[] = SQLITE_FILE_HEADER;
/*
** Set this global variable to 1 to enable tracing using the TRACE
** macro.
*/
#if SQLITE_TEST
int sqlite3_btree_trace=0; /* True to enable tracing */
#endif
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** A flag to indicate whether or not shared cache is enabled. Also,
** a list of BtShared objects that are eligible for participation
** in shared cache. The variables have file scope during normal builds,
** but the test harness needs to access these variables so we make them
** global for test builds.
*/
#ifdef SQLITE_TEST
BtShared *sqlite3SharedCacheList = 0;
int sqlite3SharedCacheEnabled = 0;
#else
static BtShared *sqlite3SharedCacheList = 0;
static int sqlite3SharedCacheEnabled = 0;
#endif
#endif /* SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Enable or disable the shared pager and schema features.
**
** This routine has no effect on existing database connections.
** The shared cache setting effects only future calls to
** sqlite3_open(), sqlite3_open16(), or sqlite3_open_v2().
*/
int sqlite3_enable_shared_cache(int enable){
sqlite3SharedCacheEnabled = enable;
return SQLITE_OK;
}
#endif
/*
** Forward declaration
*/
static int checkReadLocks(Btree*,Pgno,BtCursor*);
#ifdef SQLITE_OMIT_SHARED_CACHE
/*
** The functions queryTableLock(), lockTable() and unlockAllTables()
** manipulate entries in the BtShared.pLock linked list used to store
** shared-cache table level locks. If the library is compiled with the
** shared-cache feature disabled, then there is only ever one user
** of each BtShared structure and so this locking is not necessary.
** So define the lock related functions as no-ops.
*/
#define queryTableLock(a,b,c) SQLITE_OK
#define lockTable(a,b,c) SQLITE_OK
#define unlockAllTables(a)
#endif
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Query to see if btree handle p may obtain a lock of type eLock
** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return
** SQLITE_OK if the lock may be obtained (by calling lockTable()), or
** SQLITE_LOCKED if not.
*/
static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){
BtShared *pBt = p->pBt;
BtLock *pIter;
assert( sqlite3BtreeHoldsMutex(p) );
/* This is a no-op if the shared-cache is not enabled */
if( !p->sharable ){
return SQLITE_OK;
}
/* This (along with lockTable()) is where the ReadUncommitted flag is
** dealt with. If the caller is querying for a read-lock and the flag is
** set, it is unconditionally granted - even if there are write-locks
** on the table. If a write-lock is requested, the ReadUncommitted flag
** is not considered.
**
** In function lockTable(), if a read-lock is demanded and the
** ReadUncommitted flag is set, no entry is added to the locks list
** (BtShared.pLock).
**
** To summarize: If the ReadUncommitted flag is set, then read cursors do
** not create or respect table locks. The locking procedure for a
** write-cursor does not change.
*/
if(
!p->pSqlite ||
0==(p->pSqlite->flags&SQLITE_ReadUncommitted) ||
eLock==WRITE_LOCK ||
iTab==MASTER_ROOT
){
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->pBtree!=p && pIter->iTable==iTab &&
(pIter->eLock!=eLock || eLock!=READ_LOCK) ){
return SQLITE_LOCKED;
}
}
}
return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Add a lock on the table with root-page iTable to the shared-btree used
** by Btree handle p. Parameter eLock must be either READ_LOCK or
** WRITE_LOCK.
**
** SQLITE_OK is returned if the lock is added successfully. SQLITE_BUSY and
** SQLITE_NOMEM may also be returned.
*/
static int lockTable(Btree *p, Pgno iTable, u8 eLock){
BtShared *pBt = p->pBt;
BtLock *pLock = 0;
BtLock *pIter;
assert( sqlite3BtreeHoldsMutex(p) );
/* This is a no-op if the shared-cache is not enabled */
if( !p->sharable ){
return SQLITE_OK;
}
assert( SQLITE_OK==queryTableLock(p, iTable, eLock) );
/* If the read-uncommitted flag is set and a read-lock is requested,
** return early without adding an entry to the BtShared.pLock list. See
** comment in function queryTableLock() for more info on handling
** the ReadUncommitted flag.
*/
if(
(p->pSqlite) &&
(p->pSqlite->flags&SQLITE_ReadUncommitted) &&
(eLock==READ_LOCK) &&
iTable!=MASTER_ROOT
){
return SQLITE_OK;
}
/* First search the list for an existing lock on this table. */
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->iTable==iTable && pIter->pBtree==p ){
pLock = pIter;
break;
}
}
/* If the above search did not find a BtLock struct associating Btree p
** with table iTable, allocate one and link it into the list.
*/
if( !pLock ){
pLock = (BtLock *)sqlite3MallocZero(sizeof(BtLock));
if( !pLock ){
return SQLITE_NOMEM;
}
pLock->iTable = iTable;
pLock->pBtree = p;
pLock->pNext = pBt->pLock;
pBt->pLock = pLock;
}
/* Set the BtLock.eLock variable to the maximum of the current lock
** and the requested lock. This means if a write-lock was already held
** and a read-lock requested, we don't incorrectly downgrade the lock.
*/
assert( WRITE_LOCK>READ_LOCK );
if( eLock>pLock->eLock ){
pLock->eLock = eLock;
}
return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Release all the table locks (locks obtained via calls to the lockTable()
** procedure) held by Btree handle p.
*/
static void unlockAllTables(Btree *p){
BtLock **ppIter = &p->pBt->pLock;
assert( sqlite3BtreeHoldsMutex(p) );
assert( p->sharable || 0==*ppIter );
while( *ppIter ){
BtLock *pLock = *ppIter;
if( pLock->pBtree==p ){
*ppIter = pLock->pNext;
sqlite3_free(pLock);
}else{
ppIter = &pLock->pNext;
}
}
}
#endif /* SQLITE_OMIT_SHARED_CACHE */
static void releasePage(MemPage *pPage); /* Forward reference */
/*
** Verify that the cursor holds a mutex on the BtShared
*/
#ifndef NDEBUG
static int cursorHoldsMutex(BtCursor *p){
return sqlite3_mutex_held(p->pBt->mutex);
}
#endif
#ifndef SQLITE_OMIT_INCRBLOB
/*
** Invalidate the overflow page-list cache for cursor pCur, if any.
*/
static void invalidateOverflowCache(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
sqlite3_free(pCur->aOverflow);
pCur->aOverflow = 0;
}
/*
** Invalidate the overflow page-list cache for all cursors opened
** on the shared btree structure pBt.
*/
static void invalidateAllOverflowCache(BtShared *pBt){
BtCursor *p;
assert( sqlite3_mutex_held(pBt->mutex) );
for(p=pBt->pCursor; p; p=p->pNext){
invalidateOverflowCache(p);
}
}
#else
#define invalidateOverflowCache(x)
#define invalidateAllOverflowCache(x)
#endif
/*
** Save the current cursor position in the variables BtCursor.nKey
** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
*/
static int saveCursorPosition(BtCursor *pCur){
int rc;
assert( CURSOR_VALID==pCur->eState );
assert( 0==pCur->pKey );
assert( cursorHoldsMutex(pCur) );
rc = sqlite3BtreeKeySize(pCur, &pCur->nKey);
/* If this is an intKey table, then the above call to BtreeKeySize()
** stores the integer key in pCur->nKey. In this case this value is
** all that is required. Otherwise, if pCur is not open on an intKey
** table, then malloc space for and store the pCur->nKey bytes of key
** data.
*/
if( rc==SQLITE_OK && 0==pCur->pPage->intKey){
void *pKey = sqlite3_malloc(pCur->nKey);
if( pKey ){
rc = sqlite3BtreeKey(pCur, 0, pCur->nKey, pKey);
if( rc==SQLITE_OK ){
pCur->pKey = pKey;
}else{
sqlite3_free(pKey);
}
}else{
rc = SQLITE_NOMEM;
}
}
assert( !pCur->pPage->intKey || !pCur->pKey );
if( rc==SQLITE_OK ){
releasePage(pCur->pPage);
pCur->pPage = 0;
pCur->eState = CURSOR_REQUIRESEEK;
}
invalidateOverflowCache(pCur);
return rc;
}
/*
** Save the positions of all cursors except pExcept open on the table
** with root-page iRoot. Usually, this is called just before cursor
** pExcept is used to modify the table (BtreeDelete() or BtreeInsert()).
*/
static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
BtCursor *p;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pExcept==0 || pExcept->pBt==pBt );
for(p=pBt->pCursor; p; p=p->pNext){
if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) &&
p->eState==CURSOR_VALID ){
int rc = saveCursorPosition(p);
if( SQLITE_OK!=rc ){
return rc;
}
}
}
return SQLITE_OK;
}
/*
** Clear the current cursor position.
*/
static void clearCursorPosition(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
sqlite3_free(pCur->pKey);
pCur->pKey = 0;
pCur->eState = CURSOR_INVALID;
}
/*
** Restore the cursor to the position it was in (or as close to as possible)
** when saveCursorPosition() was called. Note that this call deletes the
** saved position info stored by saveCursorPosition(), so there can be
** at most one effective restoreOrClearCursorPosition() call after each
** saveCursorPosition().
**
** If the second argument argument - doSeek - is false, then instead of
** returning the cursor to it's saved position, any saved position is deleted
** and the cursor state set to CURSOR_INVALID.
*/
int sqlite3BtreeRestoreOrClearCursorPosition(BtCursor *pCur){
int rc;
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState>=CURSOR_REQUIRESEEK );
if( pCur->eState==CURSOR_FAULT ){
return pCur->skip;
}
#ifndef SQLITE_OMIT_INCRBLOB
if( pCur->isIncrblobHandle ){
return SQLITE_ABORT;
}
#endif
pCur->eState = CURSOR_INVALID;
rc = sqlite3BtreeMoveto(pCur, pCur->pKey, pCur->nKey, 0, &pCur->skip);
if( rc==SQLITE_OK ){
sqlite3_free(pCur->pKey);
pCur->pKey = 0;
assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_INVALID );
}
return rc;
}
#define restoreOrClearCursorPosition(p) \
(p->eState>=CURSOR_REQUIRESEEK ? \
sqlite3BtreeRestoreOrClearCursorPosition(p) : \
SQLITE_OK)
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Given a page number of a regular database page, return the page
** number for the pointer-map page that contains the entry for the
** input page number.
*/
static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
int nPagesPerMapPage, iPtrMap, ret;
assert( sqlite3_mutex_held(pBt->mutex) );
nPagesPerMapPage = (pBt->usableSize/5)+1;
iPtrMap = (pgno-2)/nPagesPerMapPage;
ret = (iPtrMap*nPagesPerMapPage) + 2;
if( ret==PENDING_BYTE_PAGE(pBt) ){
ret++;
}
return ret;
}
/*
** Write an entry into the pointer map.
**
** This routine updates the pointer map entry for page number 'key'
** so that it maps to type 'eType' and parent page number 'pgno'.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent){
DbPage *pDbPage; /* The pointer map page */
u8 *pPtrmap; /* The pointer map data */
Pgno iPtrmap; /* The pointer map page number */
int offset; /* Offset in pointer map page */
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
/* The master-journal page number must never be used as a pointer map page */
assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );
assert( pBt->autoVacuum );
if( key==0 ){
return SQLITE_CORRUPT_BKPT;
}
iPtrmap = PTRMAP_PAGENO(pBt, key);
rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
offset = PTRMAP_PTROFFSET(pBt, key);
pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
TRACE(("PTRMAP_UPDATE: %d->(%d,%d)\n", key, eType, parent));
rc = sqlite3PagerWrite(pDbPage);
if( rc==SQLITE_OK ){
pPtrmap[offset] = eType;
put4byte(&pPtrmap[offset+1], parent);
}
}
sqlite3PagerUnref(pDbPage);
return rc;
}
/*
** Read an entry from the pointer map.
**
** This routine retrieves the pointer map entry for page 'key', writing
** the type and parent page number to *pEType and *pPgno respectively.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
DbPage *pDbPage; /* The pointer map page */
int iPtrmap; /* Pointer map page index */
u8 *pPtrmap; /* Pointer map page data */
int offset; /* Offset of entry in pointer map */
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
iPtrmap = PTRMAP_PAGENO(pBt, key);
rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
if( rc!=0 ){
return rc;
}
pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
offset = PTRMAP_PTROFFSET(pBt, key);
assert( pEType!=0 );
*pEType = pPtrmap[offset];
if( pPgno ) *pPgno = get4byte(&pPtrmap[offset+1]);
sqlite3PagerUnref(pDbPage);
if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_BKPT;
return SQLITE_OK;
}
#endif /* SQLITE_OMIT_AUTOVACUUM */
/*
** Given a btree page and a cell index (0 means the first cell on
** the page, 1 means the second cell, and so forth) return a pointer
** to the cell content.
**
** This routine works only for pages that do not contain overflow cells.
*/
#define findCell(pPage, iCell) \
((pPage)->aData + get2byte(&(pPage)->aData[(pPage)->cellOffset+2*(iCell)]))
#ifdef SQLITE_TEST
u8 *sqlite3BtreeFindCell(MemPage *pPage, int iCell){
assert( iCell>=0 );
assert( iCell<get2byte(&pPage->aData[pPage->hdrOffset+3]) );
return findCell(pPage, iCell);
}
#endif
/*
** This a more complex version of sqlite3BtreeFindCell() that works for
** pages that do contain overflow cells. See insert
*/
static u8 *findOverflowCell(MemPage *pPage, int iCell){
int i;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
for(i=pPage->nOverflow-1; i>=0; i--){
int k;
struct _OvflCell *pOvfl;
pOvfl = &pPage->aOvfl[i];
k = pOvfl->idx;
if( k<=iCell ){
if( k==iCell ){
return pOvfl->pCell;
}
iCell--;
}
}
return findCell(pPage, iCell);
}
/*
** Parse a cell content block and fill in the CellInfo structure. There
** are two versions of this function. sqlite3BtreeParseCell() takes a
** cell index as the second argument and sqlite3BtreeParseCellPtr()
** takes a pointer to the body of the cell as its second argument.
**
** Within this file, the parseCell() macro can be called instead of
** sqlite3BtreeParseCellPtr(). Using some compilers, this will be faster.
*/
void sqlite3BtreeParseCellPtr(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
int n; /* Number bytes in cell content header */
u32 nPayload; /* Number of bytes of cell payload */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pInfo->pCell = pCell;
assert( pPage->leaf==0 || pPage->leaf==1 );
n = pPage->childPtrSize;
assert( n==4-4*pPage->leaf );
if( pPage->hasData ){
n += getVarint32(&pCell[n], &nPayload);
}else{
nPayload = 0;
}
pInfo->nData = nPayload;
if( pPage->intKey ){
n += getVarint(&pCell[n], (u64 *)&pInfo->nKey);
}else{
u32 x;
n += getVarint32(&pCell[n], &x);
pInfo->nKey = x;
nPayload += x;
}
pInfo->nPayload = nPayload;
pInfo->nHeader = n;
if( nPayload<=pPage->maxLocal ){
/* This is the (easy) common case where the entire payload fits
** on the local page. No overflow is required.
*/
int nSize; /* Total size of cell content in bytes */
pInfo->nLocal = nPayload;
pInfo->iOverflow = 0;
nSize = nPayload + n;
if( nSize<4 ){
nSize = 4; /* Minimum cell size is 4 */
}
pInfo->nSize = nSize;
}else{
/* If the payload will not fit completely on the local page, we have
** to decide how much to store locally and how much to spill onto
** overflow pages. The strategy is to minimize the amount of unused
** space on overflow pages while keeping the amount of local storage
** in between minLocal and maxLocal.
**
** Warning: changing the way overflow payload is distributed in any
** way will result in an incompatible file format.
*/
int minLocal; /* Minimum amount of payload held locally */
int maxLocal; /* Maximum amount of payload held locally */
int surplus; /* Overflow payload available for local storage */
minLocal = pPage->minLocal;
maxLocal = pPage->maxLocal;
surplus = minLocal + (nPayload - minLocal)%(pPage->pBt->usableSize - 4);
if( surplus <= maxLocal ){
pInfo->nLocal = surplus;
}else{
pInfo->nLocal = minLocal;
}
pInfo->iOverflow = pInfo->nLocal + n;
pInfo->nSize = pInfo->iOverflow + 4;
}
}
#define parseCell(pPage, iCell, pInfo) \
sqlite3BtreeParseCellPtr((pPage), findCell((pPage), (iCell)), (pInfo))
void sqlite3BtreeParseCell(
MemPage *pPage, /* Page containing the cell */
int iCell, /* The cell index. First cell is 0 */
CellInfo *pInfo /* Fill in this structure */
){
parseCell(pPage, iCell, pInfo);
}
/*
** Compute the total number of bytes that a Cell needs in the cell
** data area of the btree-page. The return number includes the cell
** data header and the local payload, but not any overflow page or
** the space used by the cell pointer.
*/
#ifndef NDEBUG
static int cellSize(MemPage *pPage, int iCell){
CellInfo info;
sqlite3BtreeParseCell(pPage, iCell, &info);
return info.nSize;
}
#endif
static int cellSizePtr(MemPage *pPage, u8 *pCell){
CellInfo info;
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
return info.nSize;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** If the cell pCell, part of page pPage contains a pointer
** to an overflow page, insert an entry into the pointer-map
** for the overflow page.
*/
static int ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell){
if( pCell ){
CellInfo info;
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
assert( (info.nData+(pPage->intKey?0:info.nKey))==info.nPayload );
if( (info.nData+(pPage->intKey?0:info.nKey))>info.nLocal ){
Pgno ovfl = get4byte(&pCell[info.iOverflow]);
return ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno);
}
}
return SQLITE_OK;
}
/*
** If the cell with index iCell on page pPage contains a pointer
** to an overflow page, insert an entry into the pointer-map
** for the overflow page.
*/
static int ptrmapPutOvfl(MemPage *pPage, int iCell){
u8 *pCell;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pCell = findOverflowCell(pPage, iCell);
return ptrmapPutOvflPtr(pPage, pCell);
}
#endif
/*
** Defragment the page given. All Cells are moved to the
** end of the page and all free space is collected into one
** big FreeBlk that occurs in between the header and cell
** pointer array and the cell content area.
*/
static int defragmentPage(MemPage *pPage){
int i; /* Loop counter */
int pc; /* Address of a i-th cell */
int addr; /* Offset of first byte after cell pointer array */
int hdr; /* Offset to the page header */
int size; /* Size of a cell */
int usableSize; /* Number of usable bytes on a page */
int cellOffset; /* Offset to the cell pointer array */
int brk; /* Offset to the cell content area */
int nCell; /* Number of cells on the page */
unsigned char *data; /* The page data */
unsigned char *temp; /* Temp area for cell content */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt!=0 );
assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
assert( pPage->nOverflow==0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
temp = sqlite3_malloc( pPage->pBt->pageSize );
if( temp==0 ) return SQLITE_NOMEM;
data = pPage->aData;
hdr = pPage->hdrOffset;
cellOffset = pPage->cellOffset;
nCell = pPage->nCell;
assert( nCell==get2byte(&data[hdr+3]) );
usableSize = pPage->pBt->usableSize;
brk = get2byte(&data[hdr+5]);
memcpy(&temp[brk], &data[brk], usableSize - brk);
brk = usableSize;
for(i=0; i<nCell; i++){
u8 *pAddr; /* The i-th cell pointer */
pAddr = &data[cellOffset + i*2];
pc = get2byte(pAddr);
assert( pc<pPage->pBt->usableSize );
size = cellSizePtr(pPage, &temp[pc]);
brk -= size;
memcpy(&data[brk], &temp[pc], size);
put2byte(pAddr, brk);
}
assert( brk>=cellOffset+2*nCell );
put2byte(&data[hdr+5], brk);
data[hdr+1] = 0;
data[hdr+2] = 0;
data[hdr+7] = 0;
addr = cellOffset+2*nCell;
memset(&data[addr], 0, brk-addr);
sqlite3_free(temp);
return SQLITE_OK;
}
/*
** Allocate nByte bytes of space on a page.
**
** Return the index into pPage->aData[] of the first byte of
** the new allocation. Or return 0 if there is not enough free
** space on the page to satisfy the allocation request.
**
** If the page contains nBytes of free space but does not contain
** nBytes of contiguous free space, then this routine automatically
** calls defragementPage() to consolidate all free space before
** allocating the new chunk.
*/
static int allocateSpace(MemPage *pPage, int nByte){
int addr, pc, hdr;
int size;
int nFrag;
int top;
int nCell;
int cellOffset;
unsigned char *data;
data = pPage->aData;
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
if( nByte<4 ) nByte = 4;
if( pPage->nFree<nByte || pPage->nOverflow>0 ) return 0;
pPage->nFree -= nByte;
hdr = pPage->hdrOffset;
nFrag = data[hdr+7];
if( nFrag<60 ){
/* Search the freelist looking for a slot big enough to satisfy the
** space request. */
addr = hdr+1;
while( (pc = get2byte(&data[addr]))>0 ){
size = get2byte(&data[pc+2]);
if( size>=nByte ){
if( size<nByte+4 ){
memcpy(&data[addr], &data[pc], 2);
data[hdr+7] = nFrag + size - nByte;
return pc;
}else{
put2byte(&data[pc+2], size-nByte);
return pc + size - nByte;
}
}
addr = pc;
}
}
/* Allocate memory from the gap in between the cell pointer array
** and the cell content area.
*/
top = get2byte(&data[hdr+5]);
nCell = get2byte(&data[hdr+3]);
cellOffset = pPage->cellOffset;
if( nFrag>=60 || cellOffset + 2*nCell > top - nByte ){
if( defragmentPage(pPage) ) return 0;
top = get2byte(&data[hdr+5]);
}
top -= nByte;
assert( cellOffset + 2*nCell <= top );
put2byte(&data[hdr+5], top);
return top;
}
/*
** Return a section of the pPage->aData to the freelist.
** The first byte of the new free block is pPage->aDisk[start]
** and the size of the block is "size" bytes.
**
** Most of the effort here is involved in coalesing adjacent
** free blocks into a single big free block.
*/
static void freeSpace(MemPage *pPage, int start, int size){
int addr, pbegin, hdr;
unsigned char *data = pPage->aData;
assert( pPage->pBt!=0 );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
assert( (start + size)<=pPage->pBt->usableSize );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
if( size<4 ) size = 4;
#ifdef SQLITE_SECURE_DELETE
/* Overwrite deleted information with zeros when the SECURE_DELETE
** option is enabled at compile-time */
memset(&data[start], 0, size);
#endif
/* Add the space back into the linked list of freeblocks */
hdr = pPage->hdrOffset;
addr = hdr + 1;
while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
assert( pbegin<=pPage->pBt->usableSize-4 );
assert( pbegin>addr );
addr = pbegin;
}
assert( pbegin<=pPage->pBt->usableSize-4 );
assert( pbegin>addr || pbegin==0 );
put2byte(&data[addr], start);
put2byte(&data[start], pbegin);
put2byte(&data[start+2], size);
pPage->nFree += size;
/* Coalesce adjacent free blocks */
addr = pPage->hdrOffset + 1;
while( (pbegin = get2byte(&data[addr]))>0 ){
int pnext, psize;
assert( pbegin>addr );
assert( pbegin<=pPage->pBt->usableSize-4 );
pnext = get2byte(&data[pbegin]);
psize = get2byte(&data[pbegin+2]);
if( pbegin + psize + 3 >= pnext && pnext>0 ){
int frag = pnext - (pbegin+psize);
assert( frag<=data[pPage->hdrOffset+7] );
data[pPage->hdrOffset+7] -= frag;
put2byte(&data[pbegin], get2byte(&data[pnext]));
put2byte(&data[pbegin+2], pnext+get2byte(&data[pnext+2])-pbegin);
}else{
addr = pbegin;
}
}
/* If the cell content area begins with a freeblock, remove it. */
if( data[hdr+1]==data[hdr+5] && data[hdr+2]==data[hdr+6] ){
int top;
pbegin = get2byte(&data[hdr+1]);
memcpy(&data[hdr+1], &data[pbegin], 2);
top = get2byte(&data[hdr+5]);
put2byte(&data[hdr+5], top + get2byte(&data[pbegin+2]));
}
}
/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
*/
static void decodeFlags(MemPage *pPage, int flagByte){
BtShared *pBt; /* A copy of pPage->pBt */
assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->intKey = (flagByte & (PTF_INTKEY|PTF_LEAFDATA))!=0;
pPage->zeroData = (flagByte & PTF_ZERODATA)!=0;
pPage->leaf = (flagByte & PTF_LEAF)!=0;
pPage->childPtrSize = 4*(pPage->leaf==0);
pBt = pPage->pBt;
if( flagByte & PTF_LEAFDATA ){
pPage->leafData = 1;
pPage->maxLocal = pBt->maxLeaf;
pPage->minLocal = pBt->minLeaf;
}else{
pPage->leafData = 0;
pPage->maxLocal = pBt->maxLocal;
pPage->minLocal = pBt->minLocal;
}
pPage->hasData = !(pPage->zeroData || (!pPage->leaf && pPage->leafData));
}
/*
** Initialize the auxiliary information for a disk block.
**
** The pParent parameter must be a pointer to the MemPage which
** is the parent of the page being initialized. The root of a
** BTree has no parent and so for that page, pParent==NULL.
**
** Return SQLITE_OK on success. If we see that the page does
** not contain a well-formed database page, then return
** SQLITE_CORRUPT. Note that a return of SQLITE_OK does not
** guarantee that the page is well-formed. It only shows that
** we failed to detect any corruption.
*/
int sqlite3BtreeInitPage(
MemPage *pPage, /* The page to be initialized */
MemPage *pParent /* The parent. Might be NULL */
){
int pc; /* Address of a freeblock within pPage->aData[] */
int hdr; /* Offset to beginning of page header */
u8 *data; /* Equal to pPage->aData */
BtShared *pBt; /* The main btree structure */
int usableSize; /* Amount of usable space on each page */
int cellOffset; /* Offset from start of page to first cell pointer */
int nFree; /* Number of unused bytes on the page */
int top; /* First byte of the cell content area */
pBt = pPage->pBt;
assert( pBt!=0 );
assert( pParent==0 || pParent->pBt==pBt );
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
if( pPage->pParent!=pParent && (pPage->pParent!=0 || pPage->isInit) ){
/* The parent page should never change unless the file is corrupt */
return SQLITE_CORRUPT_BKPT;
}
if( pPage->isInit ) return SQLITE_OK;
if( pPage->pParent==0 && pParent!=0 ){
pPage->pParent = pParent;
sqlite3PagerRef(pParent->pDbPage);
}
hdr = pPage->hdrOffset;
data = pPage->aData;
decodeFlags(pPage, data[hdr]);
pPage->nOverflow = 0;
pPage->idxShift = 0;
usableSize = pBt->usableSize;
pPage->cellOffset = cellOffset = hdr + 12 - 4*pPage->leaf;
top = get2byte(&data[hdr+5]);
pPage->nCell = get2byte(&data[hdr+3]);
if( pPage->nCell>MX_CELL(pBt) ){
/* To many cells for a single page. The page must be corrupt */
return SQLITE_CORRUPT_BKPT;
}
if( pPage->nCell==0 && pParent!=0 && pParent->pgno!=1 ){
/* All pages must have at least one cell, except for root pages */
return SQLITE_CORRUPT_BKPT;
}
/* Compute the total free space on the page */
pc = get2byte(&data[hdr+1]);
nFree = data[hdr+7] + top - (cellOffset + 2*pPage->nCell);
while( pc>0 ){
int next, size;
if( pc>usableSize-4 ){
/* Free block is off the page */
return SQLITE_CORRUPT_BKPT;
}
next = get2byte(&data[pc]);
size = get2byte(&data[pc+2]);
if( next>0 && next<=pc+size+3 ){
/* Free blocks must be in accending order */
return SQLITE_CORRUPT_BKPT;
}
nFree += size;
pc = next;
}
pPage->nFree = nFree;
if( nFree>=usableSize ){
/* Free space cannot exceed total page size */
return SQLITE_CORRUPT_BKPT;
}
pPage->isInit = 1;
return SQLITE_OK;
}
/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
static void zeroPage(MemPage *pPage, int flags){
unsigned char *data = pPage->aData;
BtShared *pBt = pPage->pBt;
int hdr = pPage->hdrOffset;
int first;
assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno );
assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
assert( sqlite3PagerGetData(pPage->pDbPage) == data );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( sqlite3_mutex_held(pBt->mutex) );
memset(&data[hdr], 0, pBt->usableSize - hdr);
data[hdr] = flags;
first = hdr + 8 + 4*((flags&PTF_LEAF)==0);
memset(&data[hdr+1], 0, 4);
data[hdr+7] = 0;
put2byte(&data[hdr+5], pBt->usableSize);
pPage->nFree = pBt->usableSize - first;
decodeFlags(pPage, flags);
pPage->hdrOffset = hdr;
pPage->cellOffset = first;
pPage->nOverflow = 0;
pPage->idxShift = 0;
pPage->nCell = 0;
pPage->isInit = 1;
}
/*
** Get a page from the pager. Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
**
** If the noContent flag is set, it means that we do not care about
** the content of the page at this time. So do not go to the disk
** to fetch the content. Just fill in the content with zeros for now.
** If in the future we call sqlite3PagerWrite() on this page, that
** means we have started to be concerned about content and the disk
** read should occur at that point.
*/
int sqlite3BtreeGetPage(
BtShared *pBt, /* The btree */
Pgno pgno, /* Number of the page to fetch */
MemPage **ppPage, /* Return the page in this parameter */
int noContent /* Do not load page content if true */
){
int rc;
MemPage *pPage;
DbPage *pDbPage;
assert( sqlite3_mutex_held(pBt->mutex) );
rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, noContent);
if( rc ) return rc;
pPage = (MemPage *)sqlite3PagerGetExtra(pDbPage);
pPage->aData = sqlite3PagerGetData(pDbPage);
pPage->pDbPage = pDbPage;
pPage->pBt = pBt;
pPage->pgno = pgno;
pPage->hdrOffset = pPage->pgno==1 ? 100 : 0;
*ppPage = pPage;
return SQLITE_OK;
}
/*
** Get a page from the pager and initialize it. This routine
** is just a convenience wrapper around separate calls to
** sqlite3BtreeGetPage() and sqlite3BtreeInitPage().
*/
static int getAndInitPage(
BtShared *pBt, /* The database file */
Pgno pgno, /* Number of the page to get */
MemPage **ppPage, /* Write the page pointer here */
MemPage *pParent /* Parent of the page */
){
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pgno==0 ){
return SQLITE_CORRUPT_BKPT;
}
rc = sqlite3BtreeGetPage(pBt, pgno, ppPage, 0);
if( rc==SQLITE_OK && (*ppPage)->isInit==0 ){
rc = sqlite3BtreeInitPage(*ppPage, pParent);
}
return rc;
}
/*
** Release a MemPage. This should be called once for each prior
** call to sqlite3BtreeGetPage.
*/
static void releasePage(MemPage *pPage){
if( pPage ){
assert( pPage->aData );
assert( pPage->pBt );
assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
sqlite3PagerUnref(pPage->pDbPage);
}
}
/*
** This routine is called when the reference count for a page
** reaches zero. We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(DbPage *pData, int pageSize){
MemPage *pPage;
assert( (pageSize & 7)==0 );
pPage = (MemPage *)sqlite3PagerGetExtra(pData);
assert( pPage->isInit==0 || sqlite3_mutex_held(pPage->pBt->mutex) );
if( pPage->pParent ){
MemPage *pParent = pPage->pParent;
assert( pParent->pBt==pPage->pBt );
pPage->pParent = 0;
releasePage(pParent);
}
pPage->isInit = 0;
}
/*
** During a rollback, when the pager reloads information into the cache
** so that the cache is restored to its original state at the start of
** the transaction, for each page restored this routine is called.
**
** This routine needs to reset the extra data section at the end of the
** page to agree with the restored data.
*/
static void pageReinit(DbPage *pData, int pageSize){
MemPage *pPage;
assert( (pageSize & 7)==0 );
pPage = (MemPage *)sqlite3PagerGetExtra(pData);
if( pPage->isInit ){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->isInit = 0;
sqlite3BtreeInitPage(pPage, pPage->pParent);
}
}
/*
** Open a database file.
**
** zFilename is the name of the database file. If zFilename is NULL
** a new database with a random name is created. This randomly named
** database file will be deleted when sqlite3BtreeClose() is called.
** If zFilename is ":memory:" then an in-memory database is created
** that is automatically destroyed when it is closed.
*/
int sqlite3BtreeOpen(
const char *zFilename, /* Name of the file containing the BTree database */
sqlite3 *pSqlite, /* Associated database handle */
Btree **ppBtree, /* Pointer to new Btree object written here */
int flags, /* Options */
int vfsFlags /* Flags passed through to sqlite3_vfs.xOpen() */
){
sqlite3_vfs *pVfs; /* The VFS to use for this btree */
BtShared *pBt = 0; /* Shared part of btree structure */
Btree *p; /* Handle to return */
int rc = SQLITE_OK;
int nReserve;
unsigned char zDbHeader[100];
/* Set the variable isMemdb to true for an in-memory database, or
** false for a file-based database. This symbol is only required if
** either of the shared-data or autovacuum features are compiled
** into the library.
*/
#if !defined(SQLITE_OMIT_SHARED_CACHE) || !defined(SQLITE_OMIT_AUTOVACUUM)
#ifdef SQLITE_OMIT_MEMORYDB
const int isMemdb = 0;
#else
const int isMemdb = zFilename && !strcmp(zFilename, ":memory:");
#endif
#endif
assert( pSqlite!=0 );
assert( sqlite3_mutex_held(pSqlite->mutex) );
pVfs = pSqlite->pVfs;
p = sqlite3MallocZero(sizeof(Btree));
if( !p ){
return SQLITE_NOMEM;
}
p->inTrans = TRANS_NONE;
p->pSqlite = pSqlite;
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/*
** If this Btree is a candidate for shared cache, try to find an
** existing BtShared object that we can share with
*/
if( (flags & BTREE_PRIVATE)==0
&& isMemdb==0
&& (pSqlite->flags & SQLITE_Vtab)==0
&& zFilename && zFilename[0]
){
if( sqlite3SharedCacheEnabled ){
int nFullPathname = pVfs->mxPathname+1;
char *zFullPathname = (char *)sqlite3_malloc(nFullPathname);
sqlite3_mutex *mutexShared;
p->sharable = 1;
if( pSqlite ){
pSqlite->flags |= SQLITE_SharedCache;
}
if( !zFullPathname ){
sqlite3_free(p);
return SQLITE_NOMEM;
}
sqlite3OsFullPathname(pVfs, zFilename, nFullPathname, zFullPathname);
mutexShared = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER);
sqlite3_mutex_enter(mutexShared);
for(pBt=sqlite3SharedCacheList; pBt; pBt=pBt->pNext){
assert( pBt->nRef>0 );
if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager))
&& sqlite3PagerVfs(pBt->pPager)==pVfs ){
p->pBt = pBt;
pBt->nRef++;
break;
}
}
sqlite3_mutex_leave(mutexShared);
sqlite3_free(zFullPathname);
}
#ifdef SQLITE_DEBUG
else{
/* In debug mode, we mark all persistent databases as sharable
** even when they are not. This exercises the locking code and
** gives more opportunity for asserts(sqlite3_mutex_held())
** statements to find locking problems.
*/
p->sharable = 1;
}
#endif
}
#endif
if( pBt==0 ){
/*
** The following asserts make sure that structures used by the btree are
** the right size. This is to guard against size changes that result
** when compiling on a different architecture.
*/
assert( sizeof(i64)==8 || sizeof(i64)==4 );
assert( sizeof(u64)==8 || sizeof(u64)==4 );
assert( sizeof(u32)==4 );
assert( sizeof(u16)==2 );
assert( sizeof(Pgno)==4 );
pBt = sqlite3MallocZero( sizeof(*pBt) );
if( pBt==0 ){
rc = SQLITE_NOMEM;
goto btree_open_out;
}
rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename,
EXTRA_SIZE, flags, vfsFlags);
if( rc==SQLITE_OK ){
rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
}
if( rc!=SQLITE_OK ){
goto btree_open_out;
}
p->pBt = pBt;
sqlite3PagerSetDestructor(pBt->pPager, pageDestructor);
sqlite3PagerSetReiniter(pBt->pPager, pageReinit);
pBt->pCursor = 0;
pBt->pPage1 = 0;
pBt->readOnly = sqlite3PagerIsreadonly(pBt->pPager);
pBt->pageSize = get2byte(&zDbHeader[16]);
if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
|| ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
pBt->pageSize = 0;
sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize);
pBt->maxEmbedFrac = 64; /* 25% */
pBt->minEmbedFrac = 32; /* 12.5% */
pBt->minLeafFrac = 32; /* 12.5% */
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the magic name ":memory:" will create an in-memory database, then
** leave the autoVacuum mode at 0 (do not auto-vacuum), even if
** SQLITE_DEFAULT_AUTOVACUUM is true. On the other hand, if
** SQLITE_OMIT_MEMORYDB has been defined, then ":memory:" is just a
** regular file-name. In this case the auto-vacuum applies as per normal.
*/
if( zFilename && !isMemdb ){
pBt->autoVacuum = (SQLITE_DEFAULT_AUTOVACUUM ? 1 : 0);
pBt->incrVacuum = (SQLITE_DEFAULT_AUTOVACUUM==2 ? 1 : 0);
}
#endif
nReserve = 0;
}else{
nReserve = zDbHeader[20];
pBt->maxEmbedFrac = zDbHeader[21];
pBt->minEmbedFrac = zDbHeader[22];
pBt->minLeafFrac = zDbHeader[23];
pBt->pageSizeFixed = 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
pBt->incrVacuum = (get4byte(&zDbHeader[36 + 7*4])?1:0);
#endif
}
pBt->usableSize = pBt->pageSize - nReserve;
assert( (pBt->pageSize & 7)==0 ); /* 8-byte alignment of pageSize */
sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize);
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/* Add the new BtShared object to the linked list sharable BtShareds.
*/
if( p->sharable ){
sqlite3_mutex *mutexShared;
pBt->nRef = 1;
mutexShared = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER);
if( SQLITE_THREADSAFE ){
pBt->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
if( pBt->mutex==0 ){
rc = SQLITE_NOMEM;
pSqlite->mallocFailed = 0;
goto btree_open_out;
}
}
sqlite3_mutex_enter(mutexShared);
pBt->pNext = sqlite3SharedCacheList;
sqlite3SharedCacheList = pBt;
sqlite3_mutex_leave(mutexShared);
}
#endif
}
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/* If the new Btree uses a sharable pBtShared, then link the new
** Btree into the list of all sharable Btrees for the same connection.
** The list is kept in ascending order by pBt address.
*/
if( p->sharable ){
int i;
Btree *pSib;
for(i=0; i<pSqlite->nDb; i++){
if( (pSib = pSqlite->aDb[i].pBt)!=0 && pSib->sharable ){
while( pSib->pPrev ){ pSib = pSib->pPrev; }
if( p->pBt<pSib->pBt ){
p->pNext = pSib;
p->pPrev = 0;
pSib->pPrev = p;
}else{
while( pSib->pNext && pSib->pNext->pBt<p->pBt ){
pSib = pSib->pNext;
}
p->pNext = pSib->pNext;
p->pPrev = pSib;
if( p->pNext ){
p->pNext->pPrev = p;
}
pSib->pNext = p;
}
break;
}
}
}
#endif
*ppBtree = p;
btree_open_out:
if( rc!=SQLITE_OK ){
if( pBt && pBt->pPager ){
sqlite3PagerClose(pBt->pPager);
}
sqlite3_free(pBt);
sqlite3_free(p);
*ppBtree = 0;
}
return rc;
}
/*
** Decrement the BtShared.nRef counter. When it reaches zero,
** remove the BtShared structure from the sharing list. Return
** true if the BtShared.nRef counter reaches zero and return
** false if it is still positive.
*/
static int removeFromSharingList(BtShared *pBt){
#ifndef SQLITE_OMIT_SHARED_CACHE
sqlite3_mutex *pMaster;
BtShared *pList;
int removed = 0;
assert( sqlite3_mutex_notheld(pBt->mutex) );
pMaster = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER);
sqlite3_mutex_enter(pMaster);
pBt->nRef--;
if( pBt->nRef<=0 ){
if( sqlite3SharedCacheList==pBt ){
sqlite3SharedCacheList = pBt->pNext;
}else{
pList = sqlite3SharedCacheList;
while( pList && pList->pNext!=pBt ){
pList=pList->pNext;
}
if( pList ){
pList->pNext = pBt->pNext;
}
}
if( SQLITE_THREADSAFE ){
sqlite3_mutex_free(pBt->mutex);
}
removed = 1;
}
sqlite3_mutex_leave(pMaster);
return removed;
#else
return 1;
#endif
}
/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *p){
BtShared *pBt = p->pBt;
BtCursor *pCur;
/* Close all cursors opened via this handle. */
assert( sqlite3_mutex_held(p->pSqlite->mutex) );
sqlite3BtreeEnter(p);
pCur = pBt->pCursor;
while( pCur ){
BtCursor *pTmp = pCur;
pCur = pCur->pNext;
if( pTmp->pBtree==p ){
sqlite3BtreeCloseCursor(pTmp);
}
}
/* Rollback any active transaction and free the handle structure.
** The call to sqlite3BtreeRollback() drops any table-locks held by
** this handle.
*/
sqlite3BtreeRollback(p);
sqlite3BtreeLeave(p);
/* If there are still other outstanding references to the shared-btree
** structure, return now. The remainder of this procedure cleans
** up the shared-btree.
*/
assert( p->wantToLock==0 && p->locked==0 );
if( !p->sharable || removeFromSharingList(pBt) ){
/* The pBt is no longer on the sharing list, so we can access
** it without having to hold the mutex.
**
** Clean out and delete the BtShared object.
*/
assert( !pBt->pCursor );
sqlite3PagerClose(pBt->pPager);
if( pBt->xFreeSchema && pBt->pSchema ){
pBt->xFreeSchema(pBt->pSchema);
}
sqlite3_free(pBt->pSchema);
sqlite3_free(pBt);
}
#ifndef SQLITE_OMIT_SHARED_CACHE
assert( p->wantToLock==0 );
assert( p->locked==0 );
if( p->pPrev ) p->pPrev->pNext = p->pNext;
if( p->pNext ) p->pNext->pPrev = p->pPrev;
#endif
sqlite3_free(p);
return SQLITE_OK;
}
/*
** Change the busy handler callback function.
*/
int sqlite3BtreeSetBusyHandler(Btree *p, BusyHandler *pHandler){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->pSqlite->mutex) );
sqlite3BtreeEnter(p);
pBt->pBusyHandler = pHandler;
sqlite3PagerSetBusyhandler(pBt->pPager, pHandler);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
/*
** Change the limit on the number of pages allowed in the cache.
**
** The maximum number of cache pages is set to the absolute
** value of mxPage. If mxPage is negative, the pager will
** operate asynchronously - it will not stop to do fsync()s
** to insure data is written to the disk surface before
** continuing. Transactions still work if synchronous is off,
** and the database cannot be corrupted if this program
** crashes. But if the operating system crashes or there is
** an abrupt power failure when synchronous is off, the database
** could be left in an inconsistent and unrecoverable state.
** Synchronous is on by default so database corruption is not
** normally a worry.
*/
int sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->pSqlite->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetCachesize(pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
/*
** Change the way data is synced to disk in order to increase or decrease
** how well the database resists damage due to OS crashes and power
** failures. Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage) Level 2 is the default. There
** is a very low but non-zero probability of damage. Level 3 reduces the
** probability of damage to near zero but with a write performance reduction.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
int sqlite3BtreeSetSafetyLevel(Btree *p, int level, int fullSync){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->pSqlite->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetSafetyLevel(pBt->pPager, level, fullSync);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
#endif
/*
** Return TRUE if the given btree is set to safety level 1. In other
** words, return TRUE if no sync() occurs on the disk files.
*/
int sqlite3BtreeSyncDisabled(Btree *p){
BtShared *pBt = p->pBt;
int rc;
assert( sqlite3_mutex_held(p->pSqlite->mutex) );
sqlite3BtreeEnter(p);
assert( pBt && pBt->pPager );
rc = sqlite3PagerNosync(pBt->pPager);
sqlite3BtreeLeave(p);
return rc;
}
#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM)
/*
** Change the default pages size and the number of reserved bytes per page.
**
** The page size must be a power of 2 between 512 and 65536. If the page
** size supplied does not meet this constraint then the page size is not
** changed.
**
** Page sizes are constrained to be a power of two so that the region
** of the database file used for locking (beginning at PENDING_BYTE,
** the first byte past the 1GB boundary, 0x40000000) needs to occur
** at the beginning of a page.
**
** If parameter nReserve is less than zero, then the number of reserved
** bytes per page is left unchanged.
*/
int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve){
int rc = SQLITE_OK;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( pBt->pageSizeFixed ){
sqlite3BtreeLeave(p);
return SQLITE_READONLY;
}
if( nReserve<0 ){
nReserve = pBt->pageSize - pBt->usableSize;
}
if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
((pageSize-1)&pageSize)==0 ){
assert( (pageSize & 7)==0 );
assert( !pBt->pPage1 && !pBt->pCursor );
pBt->pageSize = pageSize;
rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize);
}
pBt->usableSize = pBt->pageSize - nReserve;
sqlite3BtreeLeave(p);
return rc;
}
/*
** Return the currently defined page size
*/
int sqlite3BtreeGetPageSize(Btree *p){
return p->pBt->pageSize;
}
int sqlite3BtreeGetReserve(Btree *p){
int n;
sqlite3BtreeEnter(p);
n = p->pBt->pageSize - p->pBt->usableSize;
sqlite3BtreeLeave(p);
return n;
}
/*
** Set the maximum page count for a database if mxPage is positive.
** No changes are made if mxPage is 0 or negative.
** Regardless of the value of mxPage, return the maximum page count.
*/
int sqlite3BtreeMaxPageCount(Btree *p, int mxPage){
int n;
sqlite3BtreeEnter(p);
n = sqlite3PagerMaxPageCount(p->pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return n;
}
#endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */
/*
** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
** is disabled. The default value for the auto-vacuum property is
** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
*/
int sqlite3BtreeSetAutoVacuum(Btree *p, int autoVacuum){
#ifdef SQLITE_OMIT_AUTOVACUUM
return SQLITE_READONLY;
#else
BtShared *pBt = p->pBt;
int rc = SQLITE_OK;
int av = (autoVacuum?1:0);
sqlite3BtreeEnter(p);
if( pBt->pageSizeFixed && av!=pBt->autoVacuum ){
rc = SQLITE_READONLY;
}else{
pBt->autoVacuum = av;
}
sqlite3BtreeLeave(p);
return rc;
#endif
}
/*
** Return the value of the 'auto-vacuum' property. If auto-vacuum is
** enabled 1 is returned. Otherwise 0.
*/
int sqlite3BtreeGetAutoVacuum(Btree *p){
#ifdef SQLITE_OMIT_AUTOVACUUM
return BTREE_AUTOVACUUM_NONE;
#else
int rc;
sqlite3BtreeEnter(p);
rc = (
(!p->pBt->autoVacuum)?BTREE_AUTOVACUUM_NONE:
(!p->pBt->incrVacuum)?BTREE_AUTOVACUUM_FULL:
BTREE_AUTOVACUUM_INCR
);
sqlite3BtreeLeave(p);
return rc;
#endif
}
/*
** Get a reference to pPage1 of the database file. This will
** also acquire a readlock on that file.
**
** SQLITE_OK is returned on success. If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked. SQLITE_NOMEM
** is returned if we run out of memory.
*/
static int lockBtree(BtShared *pBt){
int rc, pageSize;
MemPage *pPage1;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pBt->pPage1 ) return SQLITE_OK;
rc = sqlite3BtreeGetPage(pBt, 1, &pPage1, 0);
if( rc!=SQLITE_OK ) return rc;
/* Do some checking to help insure the file we opened really is
** a valid database file.
*/
rc = SQLITE_NOTADB;
if( sqlite3PagerPagecount(pBt->pPager)>0 ){
u8 *page1 = pPage1->aData;
if( memcmp(page1, zMagicHeader, 16)!=0 ){
goto page1_init_failed;
}
if( page1[18]>1 ){
pBt->readOnly = 1;
}
if( page1[19]>1 ){
goto page1_init_failed;
}
pageSize = get2byte(&page1[16]);
if( ((pageSize-1)&pageSize)!=0 || pageSize<512 ||
(SQLITE_MAX_PAGE_SIZE<32768 && pageSize>SQLITE_MAX_PAGE_SIZE)
){
goto page1_init_failed;
}
assert( (pageSize & 7)==0 );
pBt->pageSize = pageSize;
pBt->usableSize = pageSize - page1[20];
if( pBt->usableSize<500 ){
goto page1_init_failed;
}
pBt->maxEmbedFrac = page1[21];
pBt->minEmbedFrac = page1[22];
pBt->minLeafFrac = page1[23];
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&page1[36 + 4*4])?1:0);
pBt->incrVacuum = (get4byte(&page1[36 + 7*4])?1:0);
#endif
}
/* maxLocal is the maximum amount of payload to store locally for
** a cell. Make sure it is small enough so that at least minFanout
** cells can will fit on one page. We assume a 10-byte page header.
** Besides the payload, the cell must store:
** 2-byte pointer to the cell
** 4-byte child pointer
** 9-byte nKey value
** 4-byte nData value
** 4-byte overflow page pointer
** So a cell consists of a 2-byte poiner, a header which is as much as
** 17 bytes long, 0 to N bytes of payload, and an optional 4 byte overflow
** page pointer.
*/
pBt->maxLocal = (pBt->usableSize-12)*pBt->maxEmbedFrac/255 - 23;
pBt->minLocal = (pBt->usableSize-12)*pBt->minEmbedFrac/255 - 23;
pBt->maxLeaf = pBt->usableSize - 35;
pBt->minLeaf = (pBt->usableSize-12)*pBt->minLeafFrac/255 - 23;
if( pBt->minLocal>pBt->maxLocal || pBt->maxLocal<0 ){
goto page1_init_failed;
}
assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
pBt->pPage1 = pPage1;
return SQLITE_OK;
page1_init_failed:
releasePage(pPage1);
pBt->pPage1 = 0;
return rc;
}
/*
** This routine works like lockBtree() except that it also invokes the
** busy callback if there is lock contention.
*/
static int lockBtreeWithRetry(Btree *pRef){
int rc = SQLITE_OK;
assert( sqlite3BtreeHoldsMutex(pRef) );
if( pRef->inTrans==TRANS_NONE ){
u8 inTransaction = pRef->pBt->inTransaction;
btreeIntegrity(pRef);
rc = sqlite3BtreeBeginTrans(pRef, 0);
pRef->pBt->inTransaction = inTransaction;
pRef->inTrans = TRANS_NONE;
if( rc==SQLITE_OK ){
pRef->pBt->nTransaction--;
}
btreeIntegrity(pRef);
}
return rc;
}
/*
** If there are no outstanding cursors and we are not in the middle
** of a transaction but there is a read lock on the database, then
** this routine unrefs the first page of the database file which
** has the effect of releasing the read lock.
**
** If there are any outstanding cursors, this routine is a no-op.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(BtShared *pBt){
assert( sqlite3_mutex_held(pBt->mutex) );
if( pBt->inTransaction==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
if( sqlite3PagerRefcount(pBt->pPager)>=1 ){
if( pBt->pPage1->aData==0 ){
MemPage *pPage = pBt->pPage1;
pPage->aData = sqlite3PagerGetData(pPage->pDbPage);
pPage->pBt = pBt;
pPage->pgno = 1;
}
releasePage(pBt->pPage1);
}
pBt->pPage1 = 0;
pBt->inStmt = 0;
}
}
/*
** Create a new database by initializing the first page of the
** file.
*/
static int newDatabase(BtShared *pBt){
MemPage *pP1;
unsigned char *data;
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
if( sqlite3PagerPagecount(pBt->pPager)>0 ) return SQLITE_OK;
pP1 = pBt->pPage1;
assert( pP1!=0 );
data = pP1->aData;
rc = sqlite3PagerWrite(pP1->pDbPage);
if( rc ) return rc;
memcpy(data, zMagicHeader, sizeof(zMagicHeader));
assert( sizeof(zMagicHeader)==16 );
put2byte(&data[16], pBt->pageSize);
data[18] = 1;
data[19] = 1;
data[20] = pBt->pageSize - pBt->usableSize;
data[21] = pBt->maxEmbedFrac;
data[22] = pBt->minEmbedFrac;
data[23] = pBt->minLeafFrac;
memset(&data[24], 0, 100-24);
zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
pBt->pageSizeFixed = 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
assert( pBt->autoVacuum==1 || pBt->autoVacuum==0 );
assert( pBt->incrVacuum==1 || pBt->incrVacuum==0 );
put4byte(&data[36 + 4*4], pBt->autoVacuum);
put4byte(&data[36 + 7*4], pBt->incrVacuum);
#endif
return SQLITE_OK;
}
/*
** Attempt to start a new transaction. A write-transaction
** is started if the second argument is nonzero, otherwise a read-
** transaction. If the second argument is 2 or more and exclusive
** transaction is started, meaning that no other process is allowed
** to access the database. A preexisting transaction may not be
** upgraded to exclusive by calling this routine a second time - the
** exclusivity flag only works for a new transaction.
**
** A write-transaction must be started before attempting any
** changes to the database. None of the following routines
** will work unless a transaction is started first:
**
** sqlite3BtreeCreateTable()
** sqlite3BtreeCreateIndex()
** sqlite3BtreeClearTable()
** sqlite3BtreeDropTable()
** sqlite3BtreeInsert()
** sqlite3BtreeDelete()
** sqlite3BtreeUpdateMeta()
**
** If an initial attempt to acquire the lock fails because of lock contention
** and the database was previously unlocked, then invoke the busy handler
** if there is one. But if there was previously a read-lock, do not
** invoke the busy handler - just return SQLITE_BUSY. SQLITE_BUSY is
** returned when there is already a read-lock in order to avoid a deadlock.
**
** Suppose there are two processes A and B. A has a read lock and B has
** a reserved lock. B tries to promote to exclusive but is blocked because
** of A's read lock. A tries to promote to reserved but is blocked by B.
** One or the other of the two processes must give way or there can be
** no progress. By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
BtShared *pBt = p->pBt;
int rc = SQLITE_OK;
sqlite3BtreeEnter(p);
btreeIntegrity(p);
/* If the btree is already in a write-transaction, or it
** is already in a read-transaction and a read-transaction
** is requested, this is a no-op.
*/
if( p->inTrans==TRANS_WRITE || (p->inTrans==TRANS_READ && !wrflag) ){
goto trans_begun;
}
/* Write transactions are not possible on a read-only database */
if( pBt->readOnly && wrflag ){
rc = SQLITE_READONLY;
goto trans_begun;
}
/* If another database handle has already opened a write transaction
** on this shared-btree structure and a second write transaction is
** requested, return SQLITE_BUSY.
*/
if( pBt->inTransaction==TRANS_WRITE && wrflag ){
rc = SQLITE_BUSY;
goto trans_begun;
}
do {
if( pBt->pPage1==0 ){
rc = lockBtree(pBt);
}
if( rc==SQLITE_OK && wrflag ){
if( pBt->readOnly ){
rc = SQLITE_READONLY;
}else{
rc = sqlite3PagerBegin(pBt->pPage1->pDbPage, wrflag>1);
if( rc==SQLITE_OK ){
rc = newDatabase(pBt);
}
}
}
if( rc==SQLITE_OK ){
if( wrflag ) pBt->inStmt = 0;
}else{
unlockBtreeIfUnused(pBt);
}
}while( rc==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
sqlite3InvokeBusyHandler(pBt->pBusyHandler) );
if( rc==SQLITE_OK ){
if( p->inTrans==TRANS_NONE ){
pBt->nTransaction++;
}
p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
if( p->inTrans>pBt->inTransaction ){
pBt->inTransaction = p->inTrans;
}
}
trans_begun:
btreeIntegrity(p);
sqlite3BtreeLeave(p);
return rc;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Set the pointer-map entries for all children of page pPage. Also, if
** pPage contains cells that point to overflow pages, set the pointer
** map entries for the overflow pages as well.
*/
static int setChildPtrmaps(MemPage *pPage){
int i; /* Counter variable */
int nCell; /* Number of cells in page pPage */
int rc; /* Return code */
BtShared *pBt = pPage->pBt;
int isInitOrig = pPage->isInit;
Pgno pgno = pPage->pgno;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
rc = sqlite3BtreeInitPage(pPage, pPage->pParent);
if( rc!=SQLITE_OK ){
goto set_child_ptrmaps_out;
}
nCell = pPage->nCell;
for(i=0; i<nCell; i++){
u8 *pCell = findCell(pPage, i);
rc = ptrmapPutOvflPtr(pPage, pCell);
if( rc!=SQLITE_OK ){
goto set_child_ptrmaps_out;
}
if( !pPage->leaf ){
Pgno childPgno = get4byte(pCell);
rc = ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno);
if( rc!=SQLITE_OK ) goto set_child_ptrmaps_out;
}
}
if( !pPage->leaf ){
Pgno childPgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
rc = ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno);
}
set_child_ptrmaps_out:
pPage->isInit = isInitOrig;
return rc;
}
/*
** Somewhere on pPage, which is guarenteed to be a btree page, not an overflow
** page, is a pointer to page iFrom. Modify this pointer so that it points to
** iTo. Parameter eType describes the type of pointer to be modified, as
** follows:
**
** PTRMAP_BTREE: pPage is a btree-page. The pointer points at a child
** page of pPage.
**
** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
** page pointed to by one of the cells on pPage.
**
** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
** overflow page in the list.
*/
static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
if( eType==PTRMAP_OVERFLOW2 ){
/* The pointer is always the first 4 bytes of the page in this case. */
if( get4byte(pPage->aData)!=iFrom ){
return SQLITE_CORRUPT_BKPT;
}
put4byte(pPage->aData, iTo);
}else{
int isInitOrig = pPage->isInit;
int i;
int nCell;
sqlite3BtreeInitPage(pPage, 0);
nCell = pPage->nCell;
for(i=0; i<nCell; i++){
u8 *pCell = findCell(pPage, i);
if( eType==PTRMAP_OVERFLOW1 ){
CellInfo info;
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
if( info.iOverflow ){
if( iFrom==get4byte(&pCell[info.iOverflow]) ){
put4byte(&pCell[info.iOverflow], iTo);
break;
}
}
}else{
if( get4byte(pCell)==iFrom ){
put4byte(pCell, iTo);
break;
}
}
}
if( i==nCell ){
if( eType!=PTRMAP_BTREE ||
get4byte(&pPage->aData[pPage->hdrOffset+8])!=iFrom ){
return SQLITE_CORRUPT_BKPT;
}
put4byte(&pPage->aData[pPage->hdrOffset+8], iTo);
}
pPage->isInit = isInitOrig;
}
return SQLITE_OK;
}
/*
** Move the open database page pDbPage to location iFreePage in the
** database. The pDbPage reference remains valid.
*/
static int relocatePage(
BtShared *pBt, /* Btree */
MemPage *pDbPage, /* Open page to move */
u8 eType, /* Pointer map 'type' entry for pDbPage */
Pgno iPtrPage, /* Pointer map 'page-no' entry for pDbPage */
Pgno iFreePage /* The location to move pDbPage to */
){
MemPage *pPtrPage; /* The page that contains a pointer to pDbPage */
Pgno iDbPage = pDbPage->pgno;
Pager *pPager = pBt->pPager;
int rc;
assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 ||
eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pDbPage->pBt==pBt );
/* Move page iDbPage from it's current location to page number iFreePage */
TRACE(("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n",
iDbPage, iFreePage, iPtrPage, eType));
rc = sqlite3PagerMovepage(pPager, pDbPage->pDbPage, iFreePage);
if( rc!=SQLITE_OK ){
return rc;
}
pDbPage->pgno = iFreePage;
/* If pDbPage was a btree-page, then it may have child pages and/or cells
** that point to overflow pages. The pointer map entries for all these
** pages need to be changed.
**
** If pDbPage is an overflow page, then the first 4 bytes may store a
** pointer to a subsequent overflow page. If this is the case, then
** the pointer map needs to be updated for the subsequent overflow page.
*/
if( eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE ){
rc = setChildPtrmaps(pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
}else{
Pgno nextOvfl = get4byte(pDbPage->aData);
if( nextOvfl!=0 ){
rc = ptrmapPut(pBt, nextOvfl, PTRMAP_OVERFLOW2, iFreePage);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
/* Fix the database pointer on page iPtrPage that pointed at iDbPage so
** that it points at iFreePage. Also fix the pointer map entry for
** iPtrPage.
*/
if( eType!=PTRMAP_ROOTPAGE ){
rc = sqlite3BtreeGetPage(pBt, iPtrPage, &pPtrPage, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pPtrPage->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pPtrPage);
return rc;
}
rc = modifyPagePointer(pPtrPage, iDbPage, iFreePage, eType);
releasePage(pPtrPage);
if( rc==SQLITE_OK ){
rc = ptrmapPut(pBt, iFreePage, eType, iPtrPage);
}
}
return rc;
}
/* Forward declaration required by incrVacuumStep(). */
static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
/*
** Perform a single step of an incremental-vacuum. If successful,
** return SQLITE_OK. If there is no work to do (and therefore no
** point in calling this function again), return SQLITE_DONE.
**
** More specificly, this function attempts to re-organize the
** database so that the last page of the file currently in use
** is no longer in use.
**
** If the nFin parameter is non-zero, the implementation assumes
** that the caller will keep calling incrVacuumStep() until
** it returns SQLITE_DONE or an error, and that nFin is the
** number of pages the database file will contain after this
** process is complete.
*/
static int incrVacuumStep(BtShared *pBt, Pgno nFin){
Pgno iLastPg; /* Last page in the database */
Pgno nFreeList; /* Number of pages still on the free-list */
assert( sqlite3_mutex_held(pBt->mutex) );
iLastPg = pBt->nTrunc;
if( iLastPg==0 ){
iLastPg = sqlite3PagerPagecount(pBt->pPager);
}
if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
int rc;
u8 eType;
Pgno iPtrPage;
nFreeList = get4byte(&pBt->pPage1->aData[36]);
if( nFreeList==0 || nFin==iLastPg ){
return SQLITE_DONE;
}
rc = ptrmapGet(pBt, iLastPg, &eType, &iPtrPage);
if( rc!=SQLITE_OK ){
return rc;
}
if( eType==PTRMAP_ROOTPAGE ){
return SQLITE_CORRUPT_BKPT;
}
if( eType==PTRMAP_FREEPAGE ){
if( nFin==0 ){
/* Remove the page from the files free-list. This is not required
** if nFin is non-zero. In that case, the free-list will be
** truncated to zero after this function returns, so it doesn't
** matter if it still contains some garbage entries.
*/
Pgno iFreePg;
MemPage *pFreePg;
rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, 1);
if( rc!=SQLITE_OK ){
return rc;
}
assert( iFreePg==iLastPg );
releasePage(pFreePg);
}
} else {
Pgno iFreePg; /* Index of free page to move pLastPg to */
MemPage *pLastPg;
rc = sqlite3BtreeGetPage(pBt, iLastPg, &pLastPg, 0);
if( rc!=SQLITE_OK ){
return rc;
}
/* If nFin is zero, this loop runs exactly once and page pLastPg
** is swapped with the first free page pulled off the free list.
**
** On the other hand, if nFin is greater than zero, then keep
** looping until a free-page located within the first nFin pages
** of the file is found.
*/
do {
MemPage *pFreePg;
rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, 0, 0);
if( rc!=SQLITE_OK ){
releasePage(pLastPg);
return rc;
}
releasePage(pFreePg);
}while( nFin!=0 && iFreePg>nFin );
assert( iFreePg<iLastPg );
rc = sqlite3PagerWrite(pLastPg->pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg);
releasePage(pLastPg);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
pBt->nTrunc = iLastPg - 1;
while( pBt->nTrunc==PENDING_BYTE_PAGE(pBt)||PTRMAP_ISPAGE(pBt, pBt->nTrunc) ){
pBt->nTrunc--;
}
return SQLITE_OK;
}
/*
** A write-transaction must be opened before calling this function.
** It performs a single unit of work towards an incremental vacuum.
**
** If the incremental vacuum is finished after this function has run,
** SQLITE_DONE is returned. If it is not finished, but no error occured,
** SQLITE_OK is returned. Otherwise an SQLite error code.
*/
int sqlite3BtreeIncrVacuum(Btree *p){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
assert( pBt->inTransaction==TRANS_WRITE && p->inTrans==TRANS_WRITE );
if( !pBt->autoVacuum ){
rc = SQLITE_DONE;
}else{
invalidateAllOverflowCache(pBt);
rc = incrVacuumStep(pBt, 0);
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** This routine is called prior to sqlite3PagerCommit when a transaction
** is commited for an auto-vacuum database.
**
** If SQLITE_OK is returned, then *pnTrunc is set to the number of pages
** the database file should be truncated to during the commit process.
** i.e. the database has been reorganized so that only the first *pnTrunc
** pages are in use.
*/
static int autoVacuumCommit(BtShared *pBt, Pgno *pnTrunc){
int rc = SQLITE_OK;
Pager *pPager = pBt->pPager;
#ifndef NDEBUG
int nRef = sqlite3PagerRefcount(pPager);
#endif
assert( sqlite3_mutex_held(pBt->mutex) );
invalidateAllOverflowCache(pBt);
assert(pBt->autoVacuum);
if( !pBt->incrVacuum ){
Pgno nFin = 0;
if( pBt->nTrunc==0 ){
Pgno nFree;
Pgno nPtrmap;
const int pgsz = pBt->pageSize;
Pgno nOrig = sqlite3PagerPagecount(pBt->pPager);
if( PTRMAP_ISPAGE(pBt, nOrig) ){
return SQLITE_CORRUPT_BKPT;
}
if( nOrig==PENDING_BYTE_PAGE(pBt) ){
nOrig--;
}
nFree = get4byte(&pBt->pPage1->aData[36]);
nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+pgsz/5)/(pgsz/5);
nFin = nOrig - nFree - nPtrmap;
if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<=PENDING_BYTE_PAGE(pBt) ){
nFin--;
}
while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
nFin--;
}
}
while( rc==SQLITE_OK ){
rc = incrVacuumStep(pBt, nFin);
}
if( rc==SQLITE_DONE ){
assert(nFin==0 || pBt->nTrunc==0 || nFin<=pBt->nTrunc);
rc = SQLITE_OK;
if( pBt->nTrunc ){
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
put4byte(&pBt->pPage1->aData[32], 0);
put4byte(&pBt->pPage1->aData[36], 0);
pBt->nTrunc = nFin;
}
}
if( rc!=SQLITE_OK ){
sqlite3PagerRollback(pPager);
}
}
if( rc==SQLITE_OK ){
*pnTrunc = pBt->nTrunc;
pBt->nTrunc = 0;
}
assert( nRef==sqlite3PagerRefcount(pPager) );
return rc;
}
#endif
/*
** This routine does the first phase of a two-phase commit. This routine
** causes a rollback journal to be created (if it does not already exist)
** and populated with enough information so that if a power loss occurs
** the database can be restored to its original state by playing back
** the journal. Then the contents of the journal are flushed out to
** the disk. After the journal is safely on oxide, the changes to the
** database are written into the database file and flushed to oxide.
** At the end of this call, the rollback journal still exists on the
** disk and we are still holding all locks, so the transaction has not
** committed. See sqlite3BtreeCommit() for the second phase of the
** commit process.
**
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zMaster points to
** the name of a master journal file that should be written into the
** individual journal file, or is NULL, indicating no master journal file
** (single database transaction).
**
** When this is called, the master journal should already have been
** created, populated with this journal pointer and synced to disk.
**
** Once this is routine has returned, the only thing required to commit
** the write-transaction for this database file is to delete the journal.
*/
int sqlite3BtreeCommitPhaseOne(Btree *p, const char *zMaster){
int rc = SQLITE_OK;
if( p->inTrans==TRANS_WRITE ){
BtShared *pBt = p->pBt;
Pgno nTrunc = 0;
sqlite3BtreeEnter(p);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
rc = autoVacuumCommit(pBt, &nTrunc);
if( rc!=SQLITE_OK ){
sqlite3BtreeLeave(p);
return rc;
}
}
#endif
rc = sqlite3PagerCommitPhaseOne(pBt->pPager, zMaster, nTrunc);
sqlite3BtreeLeave(p);
}
return rc;
}
/*
** Commit the transaction currently in progress.
**
** This routine implements the second phase of a 2-phase commit. The
** sqlite3BtreeSync() routine does the first phase and should be invoked
** prior to calling this routine. The sqlite3BtreeSync() routine did
** all the work of writing information out to disk and flushing the
** contents so that they are written onto the disk platter. All this
** routine has to do is delete or truncate the rollback journal
** (which causes the transaction to commit) and drop locks.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommitPhaseTwo(Btree *p){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
btreeIntegrity(p);
/* If the handle has a write-transaction open, commit the shared-btrees
** transaction and set the shared state to TRANS_READ.
*/
if( p->inTrans==TRANS_WRITE ){
int rc;
assert( pBt->inTransaction==TRANS_WRITE );
assert( pBt->nTransaction>0 );
rc = sqlite3PagerCommitPhaseTwo(pBt->pPager);
if( rc!=SQLITE_OK ){
sqlite3BtreeLeave(p);
return rc;
}
pBt->inTransaction = TRANS_READ;
pBt->inStmt = 0;
}
unlockAllTables(p);
/* If the handle has any kind of transaction open, decrement the transaction
** count of the shared btree. If the transaction count reaches 0, set
** the shared state to TRANS_NONE. The unlockBtreeIfUnused() call below
** will unlock the pager.
*/
if( p->inTrans!=TRANS_NONE ){
pBt->nTransaction--;
if( 0==pBt->nTransaction ){
pBt->inTransaction = TRANS_NONE;
}
}
/* Set the handles current transaction state to TRANS_NONE and unlock
** the pager if this call closed the only read or write transaction.
*/
p->inTrans = TRANS_NONE;
unlockBtreeIfUnused(pBt);
btreeIntegrity(p);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
/*
** Do both phases of a commit.
*/
int sqlite3BtreeCommit(Btree *p){
int rc;
sqlite3BtreeEnter(p);
rc = sqlite3BtreeCommitPhaseOne(p, 0);
if( rc==SQLITE_OK ){
rc = sqlite3BtreeCommitPhaseTwo(p);
}
sqlite3BtreeLeave(p);
return rc;
}
#ifndef NDEBUG
/*
** Return the number of write-cursors open on this handle. This is for use
** in assert() expressions, so it is only compiled if NDEBUG is not
** defined.
**
** For the purposes of this routine, a write-cursor is any cursor that
** is capable of writing to the databse. That means the cursor was
** originally opened for writing and the cursor has not be disabled
** by having its state changed to CURSOR_FAULT.
*/
static int countWriteCursors(BtShared *pBt){
BtCursor *pCur;
int r = 0;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->wrFlag && pCur->eState!=CURSOR_FAULT ) r++;
}
return r;
}
#endif
/*
** This routine sets the state to CURSOR_FAULT and the error
** code to errCode for every cursor on BtShared that pBtree
** references.
**
** Every cursor is tripped, including cursors that belong
** to other database connections that happen to be sharing
** the cache with pBtree.
**
** This routine gets called when a rollback occurs.
** All cursors using the same cache must be tripped
** to prevent them from trying to use the btree after
** the rollback. The rollback may have deleted tables
** or moved root pages, so it is not sufficient to
** save the state of the cursor. The cursor must be
** invalidated.
*/
void sqlite3BtreeTripAllCursors(Btree *pBtree, int errCode){
BtCursor *p;
sqlite3BtreeEnter(pBtree);
for(p=pBtree->pBt->pCursor; p; p=p->pNext){
clearCursorPosition(p);
p->eState = CURSOR_FAULT;
p->skip = errCode;
}
sqlite3BtreeLeave(pBtree);
}
/*
** Rollback the transaction in progress. All cursors will be
** invalided by this operation. Any attempt to use a cursor
** that was open at the beginning of this operation will result
** in an error.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeRollback(Btree *p){
int rc;
BtShared *pBt = p->pBt;
MemPage *pPage1;
sqlite3BtreeEnter(p);
rc = saveAllCursors(pBt, 0, 0);
#ifndef SQLITE_OMIT_SHARED_CACHE
if( rc!=SQLITE_OK ){
/* This is a horrible situation. An IO or malloc() error occured whilst
** trying to save cursor positions. If this is an automatic rollback (as
** the result of a constraint, malloc() failure or IO error) then
** the cache may be internally inconsistent (not contain valid trees) so
** we cannot simply return the error to the caller. Instead, abort
** all queries that may be using any of the cursors that failed to save.
*/
sqlite3BtreeTripAllCursors(p, rc);
}
#endif
btreeIntegrity(p);
unlockAllTables(p);
if( p->inTrans==TRANS_WRITE ){
int rc2;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->nTrunc = 0;
#endif
assert( TRANS_WRITE==pBt->inTransaction );
rc2 = sqlite3PagerRollback(pBt->pPager);
if( rc2!=SQLITE_OK ){
rc = rc2;
}
/* The rollback may have destroyed the pPage1->aData value. So
** call sqlite3BtreeGetPage() on page 1 again to make
** sure pPage1->aData is set correctly. */
if( sqlite3BtreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
releasePage(pPage1);
}
assert( countWriteCursors(pBt)==0 );
pBt->inTransaction = TRANS_READ;
}
if( p->inTrans!=TRANS_NONE ){
assert( pBt->nTransaction>0 );
pBt->nTransaction--;
if( 0==pBt->nTransaction ){
pBt->inTransaction = TRANS_NONE;
}
}
p->inTrans = TRANS_NONE;
pBt->inStmt = 0;
unlockBtreeIfUnused(pBt);
btreeIntegrity(p);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Start a statement subtransaction. The subtransaction can
** can be rolled back independently of the main transaction.
** You must start a transaction before starting a subtransaction.
** The subtransaction is ended automatically if the main transaction
** commits or rolls back.
**
** Only one subtransaction may be active at a time. It is an error to try
** to start a new subtransaction if another subtransaction is already active.
**
** Statement subtransactions are used around individual SQL statements
** that are contained within a BEGIN...COMMIT block. If a constraint
** error occurs within the statement, the effect of that one statement
** can be rolled back without having to rollback the entire transaction.
*/
int sqlite3BtreeBeginStmt(Btree *p){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( (p->inTrans!=TRANS_WRITE) || pBt->inStmt ){
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}else{
assert( pBt->inTransaction==TRANS_WRITE );
rc = pBt->readOnly ? SQLITE_OK : sqlite3PagerStmtBegin(pBt->pPager);
pBt->inStmt = 1;
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Commit the statment subtransaction currently in progress. If no
** subtransaction is active, this is a no-op.
*/
int sqlite3BtreeCommitStmt(Btree *p){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( pBt->inStmt && !pBt->readOnly ){
rc = sqlite3PagerStmtCommit(pBt->pPager);
}else{
rc = SQLITE_OK;
}
pBt->inStmt = 0;
sqlite3BtreeLeave(p);
return rc;
}
/*
** Rollback the active statement subtransaction. If no subtransaction
** is active this routine is a no-op.
**
** All cursors will be invalidated by this operation. Any attempt
** to use a cursor that was open at the beginning of this operation
** will result in an error.
*/
int sqlite3BtreeRollbackStmt(Btree *p){
int rc = SQLITE_OK;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( pBt->inStmt && !pBt->readOnly ){
rc = sqlite3PagerStmtRollback(pBt->pPager);
assert( countWriteCursors(pBt)==0 );
pBt->inStmt = 0;
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Default key comparison function to be used if no comparison function
** is specified on the sqlite3BtreeCursor() call.
*/
static int dfltCompare(
void *NotUsed, /* User data is not used */
int n1, const void *p1, /* First key to compare */
int n2, const void *p2 /* Second key to compare */
){
int c;
c = memcmp(p1, p2, n1<n2 ? n1 : n2);
if( c==0 ){
c = n1 - n2;
}
return c;
}
/*
** Create a new cursor for the BTree whose root is on the page
** iTable. The act of acquiring a cursor gets a read lock on
** the database file.
**
** If wrFlag==0, then the cursor can only be used for reading.
** If wrFlag==1, then the cursor can be used for reading or for
** writing if other conditions for writing are also met. These
** are the conditions that must be met in order for writing to
** be allowed:
**
** 1: The cursor must have been opened with wrFlag==1
**
** 2: Other database connections that share the same pager cache
** but which are not in the READ_UNCOMMITTED state may not have
** cursors open with wrFlag==0 on the same table. Otherwise
** the changes made by this write cursor would be visible to
** the read cursors in the other database connection.
**
** 3: The database must be writable (not on read-only media)
**
** 4: There must be an active transaction.
**
** No checking is done to make sure that page iTable really is the
** root page of a b-tree. If it is not, then the cursor acquired
** will not work correctly.
**
** The comparison function must be logically the same for every cursor
** on a particular table. Changing the comparison function will result
** in incorrect operations. If the comparison function is NULL, a
** default comparison function is used. The comparison function is
** always ignored for INTKEY tables.
*/
static int btreeCursor(
Btree *p, /* The btree */
int iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
int (*xCmp)(void*,int,const void*,int,const void*), /* Key Comparison func */
void *pArg, /* First arg to xCompare() */
BtCursor **ppCur /* Write new cursor here */
){
int rc;
BtCursor *pCur;
BtShared *pBt = p->pBt;
assert( sqlite3BtreeHoldsMutex(p) );
*ppCur = 0;
if( wrFlag ){
if( pBt->readOnly ){
return SQLITE_READONLY;
}
if( checkReadLocks(p, iTable, 0) ){
return SQLITE_LOCKED;
}
}
if( pBt->pPage1==0 ){
rc = lockBtreeWithRetry(p);
if( rc!=SQLITE_OK ){
return rc;
}
if( pBt->readOnly && wrFlag ){
return SQLITE_READONLY;
}
}
pCur = sqlite3MallocZero( sizeof(*pCur) );
if( pCur==0 ){
rc = SQLITE_NOMEM;
goto create_cursor_exception;
}
pCur->pgnoRoot = (Pgno)iTable;
if( iTable==1 && sqlite3PagerPagecount(pBt->pPager)==0 ){
rc = SQLITE_EMPTY;
goto create_cursor_exception;
}
rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->pPage, 0);
if( rc!=SQLITE_OK ){
goto create_cursor_exception;
}
/* Now that no other errors can occur, finish filling in the BtCursor
** variables, link the cursor into the BtShared list and set *ppCur (the
** output argument to this function).
*/
pCur->xCompare = xCmp ? xCmp : dfltCompare;
pCur->pArg = pArg;
pCur->pBtree = p;
pCur->pBt = pBt;
pCur->wrFlag = wrFlag;
pCur->pNext = pBt->pCursor;
if( pCur->pNext ){
pCur->pNext->pPrev = pCur;
}
pBt->pCursor = pCur;
pCur->eState = CURSOR_INVALID;
*ppCur = pCur;
return SQLITE_OK;
create_cursor_exception:
if( pCur ){
releasePage(pCur->pPage);
sqlite3_free(pCur);
}
unlockBtreeIfUnused(pBt);
return rc;
}
int sqlite3BtreeCursor(
Btree *p, /* The btree */
int iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
int (*xCmp)(void*,int,const void*,int,const void*), /* Key Comparison func */
void *pArg, /* First arg to xCompare() */
BtCursor **ppCur /* Write new cursor here */
){
int rc;
sqlite3BtreeEnter(p);
rc = btreeCursor(p, iTable, wrFlag, xCmp, pArg, ppCur);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Close a cursor. The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite3BtreeCloseCursor(BtCursor *pCur){
BtShared *pBt = pCur->pBt;
Btree *pBtree = pCur->pBtree;
sqlite3BtreeEnter(pBtree);
clearCursorPosition(pCur);
if( pCur->pPrev ){
pCur->pPrev->pNext = pCur->pNext;
}else{
pBt->pCursor = pCur->pNext;
}
if( pCur->pNext ){
pCur->pNext->pPrev = pCur->pPrev;
}
releasePage(pCur->pPage);
unlockBtreeIfUnused(pBt);
invalidateOverflowCache(pCur);
sqlite3_free(pCur);
sqlite3BtreeLeave(pBtree);
return SQLITE_OK;
}
/*
** Make a temporary cursor by filling in the fields of pTempCur.
** The temporary cursor is not on the cursor list for the Btree.
*/
void sqlite3BtreeGetTempCursor(BtCursor *pCur, BtCursor *pTempCur){
assert( cursorHoldsMutex(pCur) );
memcpy(pTempCur, pCur, sizeof(*pCur));
pTempCur->pNext = 0;
pTempCur->pPrev = 0;
if( pTempCur->pPage ){
sqlite3PagerRef(pTempCur->pPage->pDbPage);
}
}
/*
** Delete a temporary cursor such as was made by the CreateTemporaryCursor()
** function above.
*/
void sqlite3BtreeReleaseTempCursor(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
if( pCur->pPage ){
sqlite3PagerUnref(pCur->pPage->pDbPage);
}
}
/*
** Make sure the BtCursor* given in the argument has a valid
** BtCursor.info structure. If it is not already valid, call
** sqlite3BtreeParseCell() to fill it in.
**
** BtCursor.info is a cache of the information in the current cell.
** Using this cache reduces the number of calls to sqlite3BtreeParseCell().
**
** 2007-06-25: There is a bug in some versions of MSVC that cause the
** compiler to crash when getCellInfo() is implemented as a macro.
** But there is a measureable speed advantage to using the macro on gcc
** (when less compiler optimizations like -Os or -O0 are used and the
** compiler is not doing agressive inlining.) So we use a real function
** for MSVC and a macro for everything else. Ticket #2457.
*/
#ifndef NDEBUG
static void assertCellInfo(BtCursor *pCur){
CellInfo info;
memset(&info, 0, sizeof(info));
sqlite3BtreeParseCell(pCur->pPage, pCur->idx, &info);
assert( memcmp(&info, &pCur->info, sizeof(info))==0 );
}
#else
#define assertCellInfo(x)
#endif
#ifdef _MSC_VER
/* Use a real function in MSVC to work around bugs in that compiler. */
static void getCellInfo(BtCursor *pCur){
if( pCur->info.nSize==0 ){
sqlite3BtreeParseCell(pCur->pPage, pCur->idx, &pCur->info);
}else{
assertCellInfo(pCur);
}
}
#else /* if not _MSC_VER */
/* Use a macro in all other compilers so that the function is inlined */
#define getCellInfo(pCur) \
if( pCur->info.nSize==0 ){ \
sqlite3BtreeParseCell(pCur->pPage, pCur->idx, &pCur->info); \
}else{ \
assertCellInfo(pCur); \
}
#endif /* _MSC_VER */
/*
** Set *pSize to the size of the buffer needed to hold the value of
** the key for the current entry. If the cursor is not pointing
** to a valid entry, *pSize is set to 0.
**
** For a table with the INTKEY flag set, this routine returns the key
** itself, not the number of bytes in the key.
*/
int sqlite3BtreeKeySize(BtCursor *pCur, i64 *pSize){
int rc;
assert( cursorHoldsMutex(pCur) );
rc = restoreOrClearCursorPosition(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_INVALID || pCur->eState==CURSOR_VALID );
if( pCur->eState==CURSOR_INVALID ){
*pSize = 0;
}else{
getCellInfo(pCur);
*pSize = pCur->info.nKey;
}
}
return rc;
}
/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to. Always return SQLITE_OK.
** Failure is not possible. If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
int sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){
int rc;
assert( cursorHoldsMutex(pCur) );
rc = restoreOrClearCursorPosition(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_INVALID || pCur->eState==CURSOR_VALID );
if( pCur->eState==CURSOR_INVALID ){
/* Not pointing at a valid entry - set *pSize to 0. */
*pSize = 0;
}else{
getCellInfo(pCur);
*pSize = pCur->info.nData;
}
}
return rc;
}
/*
** Given the page number of an overflow page in the database (parameter
** ovfl), this function finds the page number of the next page in the
** linked list of overflow pages. If possible, it uses the auto-vacuum
** pointer-map data instead of reading the content of page ovfl to do so.
**
** If an error occurs an SQLite error code is returned. Otherwise:
**
** Unless pPgnoNext is NULL, the page number of the next overflow
** page in the linked list is written to *pPgnoNext. If page ovfl
** is the last page in it's linked list, *pPgnoNext is set to zero.
**
** If ppPage is not NULL, *ppPage is set to the MemPage* handle
** for page ovfl. The underlying pager page may have been requested
** with the noContent flag set, so the page data accessable via
** this handle may not be trusted.
*/
static int getOverflowPage(
BtShared *pBt,
Pgno ovfl, /* Overflow page */
MemPage **ppPage, /* OUT: MemPage handle */
Pgno *pPgnoNext /* OUT: Next overflow page number */
){
Pgno next = 0;
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
/* One of these must not be NULL. Otherwise, why call this function? */
assert(ppPage || pPgnoNext);
/* If pPgnoNext is NULL, then this function is being called to obtain
** a MemPage* reference only. No page-data is required in this case.
*/
if( !pPgnoNext ){
return sqlite3BtreeGetPage(pBt, ovfl, ppPage, 1);
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/* Try to find the next page in the overflow list using the
** autovacuum pointer-map pages. Guess that the next page in
** the overflow list is page number (ovfl+1). If that guess turns
** out to be wrong, fall back to loading the data of page
** number ovfl to determine the next page number.
*/
if( pBt->autoVacuum ){
Pgno pgno;
Pgno iGuess = ovfl+1;
u8 eType;
while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
iGuess++;
}
if( iGuess<=sqlite3PagerPagecount(pBt->pPager) ){
rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
if( rc!=SQLITE_OK ){
return rc;
}
if( eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
next = iGuess;
}
}
}
#endif
if( next==0 || ppPage ){
MemPage *pPage = 0;
rc = sqlite3BtreeGetPage(pBt, ovfl, &pPage, next!=0);
assert(rc==SQLITE_OK || pPage==0);
if( next==0 && rc==SQLITE_OK ){
next = get4byte(pPage->aData);
}
if( ppPage ){
*ppPage = pPage;
}else{
releasePage(pPage);
}
}
*pPgnoNext = next;
return rc;
}
/*
** Copy data from a buffer to a page, or from a page to a buffer.
**
** pPayload is a pointer to data stored on database page pDbPage.
** If argument eOp is false, then nByte bytes of data are copied
** from pPayload to the buffer pointed at by pBuf. If eOp is true,
** then sqlite3PagerWrite() is called on pDbPage and nByte bytes
** of data are copied from the buffer pBuf to pPayload.
**
** SQLITE_OK is returned on success, otherwise an error code.
*/
static int copyPayload(
void *pPayload, /* Pointer to page data */
void *pBuf, /* Pointer to buffer */
int nByte, /* Number of bytes to copy */
int eOp, /* 0 -> copy from page, 1 -> copy to page */
DbPage *pDbPage /* Page containing pPayload */
){
if( eOp ){
/* Copy data from buffer to page (a write operation) */
int rc = sqlite3PagerWrite(pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
memcpy(pPayload, pBuf, nByte);
}else{
/* Copy data from page to buffer (a read operation) */
memcpy(pBuf, pPayload, nByte);
}
return SQLITE_OK;
}
/*
** This function is used to read or overwrite payload information
** for the entry that the pCur cursor is pointing to. If the eOp
** parameter is 0, this is a read operation (data copied into
** buffer pBuf). If it is non-zero, a write (data copied from
** buffer pBuf).
**
** A total of "amt" bytes are read or written beginning at "offset".
** Data is read to or from the buffer pBuf.
**
** This routine does not make a distinction between key and data.
** It just reads or writes bytes from the payload area. Data might
** appear on the main page or be scattered out on multiple overflow
** pages.
**
** If the BtCursor.isIncrblobHandle flag is set, and the current
** cursor entry uses one or more overflow pages, this function
** allocates space for and lazily popluates the overflow page-list
** cache array (BtCursor.aOverflow). Subsequent calls use this
** cache to make seeking to the supplied offset more efficient.
**
** Once an overflow page-list cache has been allocated, it may be
** invalidated if some other cursor writes to the same table, or if
** the cursor is moved to a different row. Additionally, in auto-vacuum
** mode, the following events may invalidate an overflow page-list cache.
**
** * An incremental vacuum,
** * A commit in auto_vacuum="full" mode,
** * Creating a table (may require moving an overflow page).
*/
static int accessPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
int offset, /* Begin reading this far into payload */
int amt, /* Read this many bytes */
unsigned char *pBuf, /* Write the bytes into this buffer */
int skipKey, /* offset begins at data if this is true */
int eOp /* zero to read. non-zero to write. */
){
unsigned char *aPayload;
int rc = SQLITE_OK;
u32 nKey;
int iIdx = 0;
MemPage *pPage = pCur->pPage; /* Btree page of current cursor entry */
BtShared *pBt = pCur->pBt; /* Btree this cursor belongs to */
assert( pPage );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
assert( offset>=0 );
assert( cursorHoldsMutex(pCur) );
getCellInfo(pCur);
aPayload = pCur->info.pCell + pCur->info.nHeader;
nKey = (pPage->intKey ? 0 : pCur->info.nKey);
if( skipKey ){
offset += nKey;
}
if( offset+amt > nKey+pCur->info.nData ){
/* Trying to read or write past the end of the data is an error */
return SQLITE_ERROR;
}
/* Check if data must be read/written to/from the btree page itself. */
if( offset<pCur->info.nLocal ){
int a = amt;
if( a+offset>pCur->info.nLocal ){
a = pCur->info.nLocal - offset;
}
rc = copyPayload(&aPayload[offset], pBuf, a, eOp, pPage->pDbPage);
offset = 0;
pBuf += a;
amt -= a;
}else{
offset -= pCur->info.nLocal;
}
if( rc==SQLITE_OK && amt>0 ){
const int ovflSize = pBt->usableSize - 4; /* Bytes content per ovfl page */
Pgno nextPage;
nextPage = get4byte(&aPayload[pCur->info.nLocal]);
#ifndef SQLITE_OMIT_INCRBLOB
/* If the isIncrblobHandle flag is set and the BtCursor.aOverflow[]
** has not been allocated, allocate it now. The array is sized at
** one entry for each overflow page in the overflow chain. The
** page number of the first overflow page is stored in aOverflow[0],
** etc. A value of 0 in the aOverflow[] array means "not yet known"
** (the cache is lazily populated).
*/
if( pCur->isIncrblobHandle && !pCur->aOverflow ){
int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
pCur->aOverflow = (Pgno *)sqlite3MallocZero(sizeof(Pgno)*nOvfl);
if( nOvfl && !pCur->aOverflow ){
rc = SQLITE_NOMEM;
}
}
/* If the overflow page-list cache has been allocated and the
** entry for the first required overflow page is valid, skip
** directly to it.
*/
if( pCur->aOverflow && pCur->aOverflow[offset/ovflSize] ){
iIdx = (offset/ovflSize);
nextPage = pCur->aOverflow[iIdx];
offset = (offset%ovflSize);
}
#endif
for( ; rc==SQLITE_OK && amt>0 && nextPage; iIdx++){
#ifndef SQLITE_OMIT_INCRBLOB
/* If required, populate the overflow page-list cache. */
if( pCur->aOverflow ){
assert(!pCur->aOverflow[iIdx] || pCur->aOverflow[iIdx]==nextPage);
pCur->aOverflow[iIdx] = nextPage;
}
#endif
if( offset>=ovflSize ){
/* The only reason to read this page is to obtain the page
** number for the next page in the overflow chain. The page
** data is not required. So first try to lookup the overflow
** page-list cache, if any, then fall back to the getOverflowPage()
** function.
*/
#ifndef SQLITE_OMIT_INCRBLOB
if( pCur->aOverflow && pCur->aOverflow[iIdx+1] ){
nextPage = pCur->aOverflow[iIdx+1];
} else
#endif
rc = getOverflowPage(pBt, nextPage, 0, &nextPage);
offset -= ovflSize;
}else{
/* Need to read this page properly. It contains some of the
** range of data that is being read (eOp==0) or written (eOp!=0).
*/
DbPage *pDbPage;
int a = amt;
rc = sqlite3PagerGet(pBt->pPager, nextPage, &pDbPage);
if( rc==SQLITE_OK ){
aPayload = sqlite3PagerGetData(pDbPage);
nextPage = get4byte(aPayload);
if( a + offset > ovflSize ){
a = ovflSize - offset;
}
rc = copyPayload(&aPayload[offset+4], pBuf, a, eOp, pDbPage);
sqlite3PagerUnref(pDbPage);
offset = 0;
amt -= a;
pBuf += a;
}
}
}
}
if( rc==SQLITE_OK && amt>0 ){
return SQLITE_CORRUPT_BKPT;
}
return rc;
}
/*
** Read part of the key associated with cursor pCur. Exactly
** "amt" bytes will be transfered into pBuf[]. The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong. An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
int rc;
assert( cursorHoldsMutex(pCur) );
rc = restoreOrClearCursorPosition(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_VALID );
assert( pCur->pPage!=0 );
if( pCur->pPage->intKey ){
return SQLITE_CORRUPT_BKPT;
}
assert( pCur->pPage->intKey==0 );
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
rc = accessPayload(pCur, offset, amt, (unsigned char*)pBuf, 0, 0);
}
return rc;
}
/*
** Read part of the data associated with cursor pCur. Exactly
** "amt" bytes will be transfered into pBuf[]. The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong. An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
int rc;
assert( cursorHoldsMutex(pCur) );
rc = restoreOrClearCursorPosition(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_VALID );
assert( pCur->pPage!=0 );
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
rc = accessPayload(pCur, offset, amt, pBuf, 1, 0);
}
return rc;
}
/*
** Return a pointer to payload information from the entry that the
** pCur cursor is pointing to. The pointer is to the beginning of
** the key if skipKey==0 and it points to the beginning of data if
** skipKey==1. The number of bytes of available key/data is written
** into *pAmt. If *pAmt==0, then the value returned will not be
** a valid pointer.
**
** This routine is an optimization. It is common for the entire key
** and data to fit on the local page and for there to be no overflow
** pages. When that is so, this routine can be used to access the
** key and data without making a copy. If the key and/or data spills
** onto overflow pages, then accessPayload() must be used to reassembly
** the key/data and copy it into a preallocated buffer.
**
** The pointer returned by this routine looks directly into the cached
** page of the database. The data might change or move the next time
** any btree routine is called.
*/
static const unsigned char *fetchPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
int *pAmt, /* Write the number of available bytes here */
int skipKey /* read beginning at data if this is true */
){
unsigned char *aPayload;
MemPage *pPage;
u32 nKey;
int nLocal;
assert( pCur!=0 && pCur->pPage!=0 );
assert( pCur->eState==CURSOR_VALID );
assert( cursorHoldsMutex(pCur) );
pPage = pCur->pPage;
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
getCellInfo(pCur);
aPayload = pCur->info.pCell;
aPayload += pCur->info.nHeader;
if( pPage->intKey ){
nKey = 0;
}else{
nKey = pCur->info.nKey;
}
if( skipKey ){
aPayload += nKey;
nLocal = pCur->info.nLocal - nKey;
}else{
nLocal = pCur->info.nLocal;
if( nLocal>nKey ){
nLocal = nKey;
}
}
*pAmt = nLocal;
return aPayload;
}
/*
** For the entry that cursor pCur is point to, return as
** many bytes of the key or data as are available on the local
** b-tree page. Write the number of available bytes into *pAmt.
**
** The pointer returned is ephemeral. The key/data may move
** or be destroyed on the next call to any Btree routine,
** including calls from other threads against the same cache.
** Hence, a mutex on the BtShared should be held prior to calling
** this routine.
**
** These routines is used to get quick access to key and data
** in the common case where no overflow pages are used.
*/
const void *sqlite3BtreeKeyFetch(BtCursor *pCur, int *pAmt){
assert( cursorHoldsMutex(pCur) );
if( pCur->eState==CURSOR_VALID ){
return (const void*)fetchPayload(pCur, pAmt, 0);
}
return 0;
}
const void *sqlite3BtreeDataFetch(BtCursor *pCur, int *pAmt){
assert( cursorHoldsMutex(pCur) );
if( pCur->eState==CURSOR_VALID ){
return (const void*)fetchPayload(pCur, pAmt, 1);
}
return 0;
}
/*
** Move the cursor down to a new child page. The newPgno argument is the
** page number of the child page to move to.
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
int rc;
MemPage *pNewPage;
MemPage *pOldPage;
BtShared *pBt = pCur->pBt;
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
rc = getAndInitPage(pBt, newPgno, &pNewPage, pCur->pPage);
if( rc ) return rc;
pNewPage->idxParent = pCur->idx;
pOldPage = pCur->pPage;
pOldPage->idxShift = 0;
releasePage(pOldPage);
pCur->pPage = pNewPage;
pCur->idx = 0;
pCur->info.nSize = 0;
if( pNewPage->nCell<1 ){
return SQLITE_CORRUPT_BKPT;
}
return SQLITE_OK;
}
/*
** Return true if the page is the virtual root of its table.
**
** The virtual root page is the root page for most tables. But
** for the table rooted on page 1, sometime the real root page
** is empty except for the right-pointer. In such cases the
** virtual root page is the page that the right-pointer of page
** 1 is pointing to.
*/
int sqlite3BtreeIsRootPage(MemPage *pPage){
MemPage *pParent;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pParent = pPage->pParent;
if( pParent==0 ) return 1;
if( pParent->pgno>1 ) return 0;
if( get2byte(&pParent->aData[pParent->hdrOffset+3])==0 ) return 1;
return 0;
}
/*
** Move the cursor up to the parent page.
**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from. If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
void sqlite3BtreeMoveToParent(BtCursor *pCur){
MemPage *pParent;
MemPage *pPage;
int idxParent;
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
pPage = pCur->pPage;
assert( pPage!=0 );
assert( !sqlite3BtreeIsRootPage(pPage) );
pParent = pPage->pParent;
assert( pParent!=0 );
idxParent = pPage->idxParent;
sqlite3PagerRef(pParent->pDbPage);
releasePage(pPage);
pCur->pPage = pParent;
pCur->info.nSize = 0;
assert( pParent->idxShift==0 );
pCur->idx = idxParent;
}
/*
** Move the cursor to the root page
*/
static int moveToRoot(BtCursor *pCur){
MemPage *pRoot;
int rc = SQLITE_OK;
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
assert( cursorHoldsMutex(pCur) );
assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
assert( CURSOR_VALID < CURSOR_REQUIRESEEK );
assert( CURSOR_FAULT > CURSOR_REQUIRESEEK );
if( pCur->eState>=CURSOR_REQUIRESEEK ){
if( pCur->eState==CURSOR_FAULT ){
return pCur->skip;
}
clearCursorPosition(pCur);
}
pRoot = pCur->pPage;
if( pRoot && pRoot->pgno==pCur->pgnoRoot ){
assert( pRoot->isInit );
}else{
if(
SQLITE_OK!=(rc = getAndInitPage(pBt, pCur->pgnoRoot, &pRoot, 0))
){
pCur->eState = CURSOR_INVALID;
return rc;
}
releasePage(pCur->pPage);
pCur->pPage = pRoot;
}
pCur->idx = 0;
pCur->info.nSize = 0;
if( pRoot->nCell==0 && !pRoot->leaf ){
Pgno subpage;
assert( pRoot->pgno==1 );
subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
assert( subpage>0 );
pCur->eState = CURSOR_VALID;
rc = moveToChild(pCur, subpage);
}
pCur->eState = ((pCur->pPage->nCell>0)?CURSOR_VALID:CURSOR_INVALID);
return rc;
}
/*
** Move the cursor down to the left-most leaf entry beneath the
** entry to which it is currently pointing.
**
** The left-most leaf is the one with the smallest key - the first
** in ascending order.
*/
static int moveToLeftmost(BtCursor *pCur){
Pgno pgno;
int rc = SQLITE_OK;
MemPage *pPage;
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
while( rc==SQLITE_OK && !(pPage = pCur->pPage)->leaf ){
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
pgno = get4byte(findCell(pPage, pCur->idx));
rc = moveToChild(pCur, pgno);
}
return rc;
}
/*
** Move the cursor down to the right-most leaf entry beneath the
** page to which it is currently pointing. Notice the difference
** between moveToLeftmost() and moveToRightmost(). moveToLeftmost()
** finds the left-most entry beneath the *entry* whereas moveToRightmost()
** finds the right-most entry beneath the *page*.
**
** The right-most entry is the one with the largest key - the last
** key in ascending order.
*/
static int moveToRightmost(BtCursor *pCur){
Pgno pgno;
int rc = SQLITE_OK;
MemPage *pPage;
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
while( rc==SQLITE_OK && !(pPage = pCur->pPage)->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
pCur->idx = pPage->nCell;
rc = moveToChild(pCur, pgno);
}
if( rc==SQLITE_OK ){
pCur->idx = pPage->nCell - 1;
pCur->info.nSize = 0;
}
return SQLITE_OK;
}
/* Move the cursor to the first entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
int rc;
assert( cursorHoldsMutex(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
rc = moveToRoot(pCur);
if( rc==SQLITE_OK ){
if( pCur->eState==CURSOR_INVALID ){
assert( pCur->pPage->nCell==0 );
*pRes = 1;
rc = SQLITE_OK;
}else{
assert( pCur->pPage->nCell>0 );
*pRes = 0;
rc = moveToLeftmost(pCur);
}
}
return rc;
}
/* Move the cursor to the last entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
int rc;
assert( cursorHoldsMutex(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
rc = moveToRoot(pCur);
if( rc==SQLITE_OK ){
if( CURSOR_INVALID==pCur->eState ){
assert( pCur->pPage->nCell==0 );
*pRes = 1;
}else{
assert( pCur->eState==CURSOR_VALID );
*pRes = 0;
rc = moveToRightmost(pCur);
}
}
return rc;
}
/* Move the cursor so that it points to an entry near pKey/nKey.
** Return a success code.
**
** For INTKEY tables, only the nKey parameter is used. pKey is
** ignored. For other tables, nKey is the number of bytes of data
** in pKey. The comparison function specified when the cursor was
** created is used to compare keys.
**
** If an exact match is not found, then the cursor is always
** left pointing at a leaf page which would hold the entry if it
** were present. The cursor might point to an entry that comes
** before or after the key.
**
** The result of comparing the key with the entry to which the
** cursor is written to *pRes if pRes!=NULL. The meaning of
** this value is as follows:
**
** *pRes<0 The cursor is left pointing at an entry that
** is smaller than pKey or if the table is empty
** and the cursor is therefore left point to nothing.
**
** *pRes==0 The cursor is left pointing at an entry that
** exactly matches pKey.
**
** *pRes>0 The cursor is left pointing at an entry that
** is larger than pKey.
**
*/
int sqlite3BtreeMoveto(
BtCursor *pCur, /* The cursor to be moved */
const void *pKey, /* The key content for indices. Not used by tables */
i64 nKey, /* Size of pKey. Or the key for tables */
int biasRight, /* If true, bias the search to the high end */
int *pRes /* Search result flag */
){
int rc;
assert( cursorHoldsMutex(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
rc = moveToRoot(pCur);
if( rc ){
return rc;
}
assert( pCur->pPage );
assert( pCur->pPage->isInit );
if( pCur->eState==CURSOR_INVALID ){
*pRes = -1;
assert( pCur->pPage->nCell==0 );
return SQLITE_OK;
}
for(;;){
int lwr, upr;
Pgno chldPg;
MemPage *pPage = pCur->pPage;
int c = -1; /* pRes return if table is empty must be -1 */
lwr = 0;
upr = pPage->nCell-1;
if( !pPage->intKey && pKey==0 ){
return SQLITE_CORRUPT_BKPT;
}
if( biasRight ){
pCur->idx = upr;
}else{
pCur->idx = (upr+lwr)/2;
}
if( lwr<=upr ) for(;;){
void *pCellKey;
i64 nCellKey;
pCur->info.nSize = 0;
if( pPage->intKey ){
u8 *pCell;
pCell = findCell(pPage, pCur->idx) + pPage->childPtrSize;
if( pPage->hasData ){
u32 dummy;
pCell += getVarint32(pCell, &dummy);
}
getVarint(pCell, (u64 *)&nCellKey);
if( nCellKey<nKey ){
c = -1;
}else if( nCellKey>nKey ){
c = +1;
}else{
c = 0;
}
}else{
int available;
pCellKey = (void *)fetchPayload(pCur, &available, 0);
nCellKey = pCur->info.nKey;
if( available>=nCellKey ){
c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
}else{
pCellKey = sqlite3_malloc( nCellKey );
if( pCellKey==0 ) return SQLITE_NOMEM;
rc = sqlite3BtreeKey(pCur, 0, nCellKey, (void *)pCellKey);
c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
sqlite3_free(pCellKey);
if( rc ){
return rc;
}
}
}
if( c==0 ){
if( pPage->leafData && !pPage->leaf ){
lwr = pCur->idx;
upr = lwr - 1;
break;
}else{
if( pRes ) *pRes = 0;
return SQLITE_OK;
}
}
if( c<0 ){
lwr = pCur->idx+1;
}else{
upr = pCur->idx-1;
}
if( lwr>upr ){
break;
}
pCur->idx = (lwr+upr)/2;
}
assert( lwr==upr+1 );
assert( pPage->isInit );
if( pPage->leaf ){
chldPg = 0;
}else if( lwr>=pPage->nCell ){
chldPg = get4byte(&pPage->aData[pPage->hdrOffset+8]);
}else{
chldPg = get4byte(findCell(pPage, lwr));
}
if( chldPg==0 ){
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
if( pRes ) *pRes = c;
return SQLITE_OK;
}
pCur->idx = lwr;
pCur->info.nSize = 0;
rc = moveToChild(pCur, chldPg);
if( rc ){
return rc;
}
}
/* NOT REACHED */
}
/*
** Return TRUE if the cursor is not pointing at an entry of the table.
**
** TRUE will be returned after a call to sqlite3BtreeNext() moves
** past the last entry in the table or sqlite3BtreePrev() moves past
** the first entry. TRUE is also returned if the table is empty.
*/
int sqlite3BtreeEof(BtCursor *pCur){
/* TODO: What if the cursor is in CURSOR_REQUIRESEEK but all table entries
** have been deleted? This API will need to change to return an error code
** as well as the boolean result value.
*/
return (CURSOR_VALID!=pCur->eState);
}
/*
** Return the database connection handle for a cursor.
*/
sqlite3 *sqlite3BtreeCursorDb(const BtCursor *pCur){
assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
return pCur->pBtree->pSqlite;
}
/*
** Advance the cursor to the next entry in the database. If
** successful then set *pRes=0. If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1.
*/
static int btreeNext(BtCursor *pCur, int *pRes){
int rc;
MemPage *pPage;
assert( cursorHoldsMutex(pCur) );
rc = restoreOrClearCursorPosition(pCur);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pRes!=0 );
pPage = pCur->pPage;
if( CURSOR_INVALID==pCur->eState ){
*pRes = 1;
return SQLITE_OK;
}
if( pCur->skip>0 ){
pCur->skip = 0;
*pRes = 0;
return SQLITE_OK;
}
pCur->skip = 0;
assert( pPage->isInit );
assert( pCur->idx<pPage->nCell );
pCur->idx++;
pCur->info.nSize = 0;
if( pCur->idx>=pPage->nCell ){
if( !pPage->leaf ){
rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
if( rc ) return rc;
rc = moveToLeftmost(pCur);
*pRes = 0;
return rc;
}
do{
if( sqlite3BtreeIsRootPage(pPage) ){
*pRes = 1;
pCur->eState = CURSOR_INVALID;
return SQLITE_OK;
}
sqlite3BtreeMoveToParent(pCur);
pPage = pCur->pPage;
}while( pCur->idx>=pPage->nCell );
*pRes = 0;
if( pPage->leafData ){
rc = sqlite3BtreeNext(pCur, pRes);
}else{
rc = SQLITE_OK;
}
return rc;
}
*pRes = 0;
if( pPage->leaf ){
return SQLITE_OK;
}
rc = moveToLeftmost(pCur);
return rc;
}
int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
int rc;
assert( cursorHoldsMutex(pCur) );
rc = btreeNext(pCur, pRes);
return rc;
}
/*
** Step the cursor to the back to the previous entry in the database. If
** successful then set *pRes=0. If the cursor
** was already pointing to the first entry in the database before
** this routine was called, then set *pRes=1.
*/
static int btreePrevious(BtCursor *pCur, int *pRes){
int rc;
Pgno pgno;
MemPage *pPage;
assert( cursorHoldsMutex(pCur) );
rc = restoreOrClearCursorPosition(pCur);
if( rc!=SQLITE_OK ){
return rc;
}
if( CURSOR_INVALID==pCur->eState ){
*pRes = 1;
return SQLITE_OK;
}
if( pCur->skip<0 ){
pCur->skip = 0;
*pRes = 0;
return SQLITE_OK;
}
pCur->skip = 0;
pPage = pCur->pPage;
assert( pPage->isInit );
assert( pCur->idx>=0 );
if( !pPage->leaf ){
pgno = get4byte( findCell(pPage, pCur->idx) );
rc = moveToChild(pCur, pgno);
if( rc ){
return rc;
}
rc = moveToRightmost(pCur);
}else{
while( pCur->idx==0 ){
if( sqlite3BtreeIsRootPage(pPage) ){
pCur->eState = CURSOR_INVALID;
*pRes = 1;
return SQLITE_OK;
}
sqlite3BtreeMoveToParent(pCur);
pPage = pCur->pPage;
}
pCur->idx--;
pCur->info.nSize = 0;
if( pPage->leafData && !pPage->leaf ){
rc = sqlite3BtreePrevious(pCur, pRes);
}else{
rc = SQLITE_OK;
}
}
*pRes = 0;
return rc;
}
int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
int rc;
assert( cursorHoldsMutex(pCur) );
rc = btreePrevious(pCur, pRes);
return rc;
}
/*
** Allocate a new page from the database file.
**
** The new page is marked as dirty. (In other words, sqlite3PagerWrite()
** has already been called on the new page.) The new page has also
** been referenced and the calling routine is responsible for calling
** sqlite3PagerUnref() on the new page when it is done.
**
** SQLITE_OK is returned on success. Any other return value indicates
** an error. *ppPage and *pPgno are undefined in the event of an error.
** Do not invoke sqlite3PagerUnref() on *ppPage if an error is returned.
**
** If the "nearby" parameter is not 0, then a (feeble) effort is made to
** locate a page close to the page number "nearby". This can be used in an
** attempt to keep related pages close to each other in the database file,
** which in turn can make database access faster.
**
** If the "exact" parameter is not 0, and the page-number nearby exists
** anywhere on the free-list, then it is guarenteed to be returned. This
** is only used by auto-vacuum databases when allocating a new table.
*/
static int allocateBtreePage(
BtShared *pBt,
MemPage **ppPage,
Pgno *pPgno,
Pgno nearby,
u8 exact
){
MemPage *pPage1;
int rc;
int n; /* Number of pages on the freelist */
int k; /* Number of leaves on the trunk of the freelist */
MemPage *pTrunk = 0;
MemPage *pPrevTrunk = 0;
assert( sqlite3_mutex_held(pBt->mutex) );
pPage1 = pBt->pPage1;
n = get4byte(&pPage1->aData[36]);
if( n>0 ){
/* There are pages on the freelist. Reuse one of those pages. */
Pgno iTrunk;
u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
/* If the 'exact' parameter was true and a query of the pointer-map
** shows that the page 'nearby' is somewhere on the free-list, then
** the entire-list will be searched for that page.
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
if( exact && nearby<=sqlite3PagerPagecount(pBt->pPager) ){
u8 eType;
assert( nearby>0 );
assert( pBt->autoVacuum );
rc = ptrmapGet(pBt, nearby, &eType, 0);
if( rc ) return rc;
if( eType==PTRMAP_FREEPAGE ){
searchList = 1;
}
*pPgno = nearby;
}
#endif
/* Decrement the free-list count by 1. Set iTrunk to the index of the
** first free-list trunk page. iPrevTrunk is initially 1.
*/
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc ) return rc;
put4byte(&pPage1->aData[36], n-1);
/* The code within this loop is run only once if the 'searchList' variable
** is not true. Otherwise, it runs once for each trunk-page on the
** free-list until the page 'nearby' is located.
*/
do {
pPrevTrunk = pTrunk;
if( pPrevTrunk ){
iTrunk = get4byte(&pPrevTrunk->aData[0]);
}else{
iTrunk = get4byte(&pPage1->aData[32]);
}
rc = sqlite3BtreeGetPage(pBt, iTrunk, &pTrunk, 0);
if( rc ){
pTrunk = 0;
goto end_allocate_page;
}
k = get4byte(&pTrunk->aData[4]);
if( k==0 && !searchList ){
/* The trunk has no leaves and the list is not being searched.
** So extract the trunk page itself and use it as the newly
** allocated page */
assert( pPrevTrunk==0 );
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
*pPgno = iTrunk;
memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
*ppPage = pTrunk;
pTrunk = 0;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
}else if( k>pBt->usableSize/4 - 8 ){
/* Value of k is out of range. Database corruption */
rc = SQLITE_CORRUPT_BKPT;
goto end_allocate_page;
#ifndef SQLITE_OMIT_AUTOVACUUM
}else if( searchList && nearby==iTrunk ){
/* The list is being searched and this trunk page is the page
** to allocate, regardless of whether it has leaves.
*/
assert( *pPgno==iTrunk );
*ppPage = pTrunk;
searchList = 0;
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
if( k==0 ){
if( !pPrevTrunk ){
memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
}else{
memcpy(&pPrevTrunk->aData[0], &pTrunk->aData[0], 4);
}
}else{
/* The trunk page is required by the caller but it contains
** pointers to free-list leaves. The first leaf becomes a trunk
** page in this case.
*/
MemPage *pNewTrunk;
Pgno iNewTrunk = get4byte(&pTrunk->aData[8]);
rc = sqlite3BtreeGetPage(pBt, iNewTrunk, &pNewTrunk, 0);
if( rc!=SQLITE_OK ){
goto end_allocate_page;
}
rc = sqlite3PagerWrite(pNewTrunk->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pNewTrunk);
goto end_allocate_page;
}
memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
put4byte(&pNewTrunk->aData[4], k-1);
memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
releasePage(pNewTrunk);
if( !pPrevTrunk ){
put4byte(&pPage1->aData[32], iNewTrunk);
}else{
rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
put4byte(&pPrevTrunk->aData[0], iNewTrunk);
}
}
pTrunk = 0;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
#endif
}else{
/* Extract a leaf from the trunk */
int closest;
Pgno iPage;
unsigned char *aData = pTrunk->aData;
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
if( nearby>0 ){
int i, dist;
closest = 0;
dist = get4byte(&aData[8]) - nearby;
if( dist<0 ) dist = -dist;
for(i=1; i<k; i++){
int d2 = get4byte(&aData[8+i*4]) - nearby;
if( d2<0 ) d2 = -d2;
if( d2<dist ){
closest = i;
dist = d2;
}
}
}else{
closest = 0;
}
iPage = get4byte(&aData[8+closest*4]);
if( !searchList || iPage==nearby ){
*pPgno = iPage;
if( *pPgno>sqlite3PagerPagecount(pBt->pPager) ){
/* Free page off the end of the file */
return SQLITE_CORRUPT_BKPT;
}
TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
": %d more free pages\n",
*pPgno, closest+1, k, pTrunk->pgno, n-1));
if( closest<k-1 ){
memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
}
put4byte(&aData[4], k-1);
rc = sqlite3BtreeGetPage(pBt, *pPgno, ppPage, 1);
if( rc==SQLITE_OK ){
sqlite3PagerDontRollback((*ppPage)->pDbPage);
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
}
}
searchList = 0;
}
}
releasePage(pPrevTrunk);
pPrevTrunk = 0;
}while( searchList );
}else{
/* There are no pages on the freelist, so create a new page at the
** end of the file */
*pPgno = sqlite3PagerPagecount(pBt->pPager) + 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->nTrunc ){
/* An incr-vacuum has already run within this transaction. So the
** page to allocate is not from the physical end of the file, but
** at pBt->nTrunc.
*/
*pPgno = pBt->nTrunc+1;
if( *pPgno==PENDING_BYTE_PAGE(pBt) ){
(*pPgno)++;
}
}
if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, *pPgno) ){
/* If *pPgno refers to a pointer-map page, allocate two new pages
** at the end of the file instead of one. The first allocated page
** becomes a new pointer-map page, the second is used by the caller.
*/
TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", *pPgno));
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
(*pPgno)++;
}
if( pBt->nTrunc ){
pBt->nTrunc = *pPgno;
}
#endif
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
rc = sqlite3BtreeGetPage(pBt, *pPgno, ppPage, 0);
if( rc ) return rc;
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
}
TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
}
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
end_allocate_page:
releasePage(pTrunk);
releasePage(pPrevTrunk);
return rc;
}
/*
** Add a page of the database file to the freelist.
**
** sqlite3PagerUnref() is NOT called for pPage.
*/
static int freePage(MemPage *pPage){
BtShared *pBt = pPage->pBt;
MemPage *pPage1 = pBt->pPage1;
int rc, n, k;
/* Prepare the page for freeing */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->pgno>1 );
pPage->isInit = 0;
releasePage(pPage->pParent);
pPage->pParent = 0;
/* Increment the free page count on pPage1 */
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc ) return rc;
n = get4byte(&pPage1->aData[36]);
put4byte(&pPage1->aData[36], n+1);
#ifdef SQLITE_SECURE_DELETE
/* If the SQLITE_SECURE_DELETE compile-time option is enabled, then
** always fully overwrite deleted information with zeros.
*/
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ) return rc;
memset(pPage->aData, 0, pPage->pBt->pageSize);
#endif
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the database supports auto-vacuum, write an entry in the pointer-map
** to indicate that the page is free.
*/
if( pBt->autoVacuum ){
rc = ptrmapPut(pBt, pPage->pgno, PTRMAP_FREEPAGE, 0);
if( rc ) return rc;
}
#endif
if( n==0 ){
/* This is the first free page */
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ) return rc;
memset(pPage->aData, 0, 8);
put4byte(&pPage1->aData[32], pPage->pgno);
TRACE(("FREE-PAGE: %d first\n", pPage->pgno));
}else{
/* Other free pages already exist. Retrive the first trunk page
** of the freelist and find out how many leaves it has. */
MemPage *pTrunk;
rc = sqlite3BtreeGetPage(pBt, get4byte(&pPage1->aData[32]), &pTrunk, 0);
if( rc ) return rc;
k = get4byte(&pTrunk->aData[4]);
if( k>=pBt->usableSize/4 - 8 ){
/* The trunk is full. Turn the page being freed into a new
** trunk page with no leaves. */
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc==SQLITE_OK ){
put4byte(pPage->aData, pTrunk->pgno);
put4byte(&pPage->aData[4], 0);
put4byte(&pPage1->aData[32], pPage->pgno);
TRACE(("FREE-PAGE: %d new trunk page replacing %d\n",
pPage->pgno, pTrunk->pgno));
}
}else if( k<0 ){
rc = SQLITE_CORRUPT;
}else{
/* Add the newly freed page as a leaf on the current trunk */
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pTrunk->aData[4], k+1);
put4byte(&pTrunk->aData[8+k*4], pPage->pgno);
#ifndef SQLITE_SECURE_DELETE
sqlite3PagerDontWrite(pPage->pDbPage);
#endif
}
TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
}
releasePage(pTrunk);
}
return rc;
}
/*
** Free any overflow pages associated with the given Cell.
*/
static int clearCell(MemPage *pPage, unsigned char *pCell){
BtShared *pBt = pPage->pBt;
CellInfo info;
Pgno ovflPgno;
int rc;
int nOvfl;
int ovflPageSize;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
if( info.iOverflow==0 ){
return SQLITE_OK; /* No overflow pages. Return without doing anything */
}
ovflPgno = get4byte(&pCell[info.iOverflow]);
ovflPageSize = pBt->usableSize - 4;
nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
assert( ovflPgno==0 || nOvfl>0 );
while( nOvfl-- ){
MemPage *pOvfl;
if( ovflPgno==0 || ovflPgno>sqlite3PagerPagecount(pBt->pPager) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getOverflowPage(pBt, ovflPgno, &pOvfl, (nOvfl==0)?0:&ovflPgno);
if( rc ) return rc;
rc = freePage(pOvfl);
sqlite3PagerUnref(pOvfl->pDbPage);
if( rc ) return rc;
}
return SQLITE_OK;
}
/*
** Create the byte sequence used to represent a cell on page pPage
** and write that byte sequence into pCell[]. Overflow pages are
** allocated and filled in as necessary. The calling procedure
** is responsible for making sure sufficient space has been allocated
** for pCell[].
**
** Note that pCell does not necessary need to point to the pPage->aData
** area. pCell might point to some temporary storage. The cell will
** be constructed in this temporary area then copied into pPage->aData
** later.
*/
static int fillInCell(
MemPage *pPage, /* The page that contains the cell */
unsigned char *pCell, /* Complete text of the cell */
const void *pKey, i64 nKey, /* The key */
const void *pData,int nData, /* The data */
int nZero, /* Extra zero bytes to append to pData */
int *pnSize /* Write cell size here */
){
int nPayload;
const u8 *pSrc;
int nSrc, n, rc;
int spaceLeft;
MemPage *pOvfl = 0;
MemPage *pToRelease = 0;
unsigned char *pPrior;
unsigned char *pPayload;
BtShared *pBt = pPage->pBt;
Pgno pgnoOvfl = 0;
int nHeader;
CellInfo info;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
/* Fill in the header. */
nHeader = 0;
if( !pPage->leaf ){
nHeader += 4;
}
if( pPage->hasData ){
nHeader += putVarint(&pCell[nHeader], nData+nZero);
}else{
nData = nZero = 0;
}
nHeader += putVarint(&pCell[nHeader], *(u64*)&nKey);
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
assert( info.nHeader==nHeader );
assert( info.nKey==nKey );
assert( info.nData==nData+nZero );
/* Fill in the payload */
nPayload = nData + nZero;
if( pPage->intKey ){
pSrc = pData;
nSrc = nData;
nData = 0;
}else{
nPayload += nKey;
pSrc = pKey;
nSrc = nKey;
}
*pnSize = info.nSize;
spaceLeft = info.nLocal;
pPayload = &pCell[nHeader];
pPrior = &pCell[info.iOverflow];
while( nPayload>0 ){
if( spaceLeft==0 ){
int isExact = 0;
#ifndef SQLITE_OMIT_AUTOVACUUM
Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
if( pBt->autoVacuum ){
do{
pgnoOvfl++;
} while(
PTRMAP_ISPAGE(pBt, pgnoOvfl) || pgnoOvfl==PENDING_BYTE_PAGE(pBt)
);
if( pgnoOvfl>1 ){
/* isExact = 1; */
}
}
#endif
rc = allocateBtreePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, isExact);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the database supports auto-vacuum, and the second or subsequent
** overflow page is being allocated, add an entry to the pointer-map
** for that page now.
**
** If this is the first overflow page, then write a partial entry
** to the pointer-map. If we write nothing to this pointer-map slot,
** then the optimistic overflow chain processing in clearCell()
** may misinterpret the uninitialised values and delete the
** wrong pages from the database.
*/
if( pBt->autoVacuum && rc==SQLITE_OK ){
u8 eType = (pgnoPtrmap?PTRMAP_OVERFLOW2:PTRMAP_OVERFLOW1);
rc = ptrmapPut(pBt, pgnoOvfl, eType, pgnoPtrmap);
if( rc ){
releasePage(pOvfl);
}
}
#endif
if( rc ){
releasePage(pToRelease);
return rc;
}
put4byte(pPrior, pgnoOvfl);
releasePage(pToRelease);
pToRelease = pOvfl;
pPrior = pOvfl->aData;
put4byte(pPrior, 0);
pPayload = &pOvfl->aData[4];
spaceLeft = pBt->usableSize - 4;
}
n = nPayload;
if( n>spaceLeft ) n = spaceLeft;
if( nSrc>0 ){
if( n>nSrc ) n = nSrc;
assert( pSrc );
memcpy(pPayload, pSrc, n);
}else{
memset(pPayload, 0, n);
}
nPayload -= n;
pPayload += n;
pSrc += n;
nSrc -= n;
spaceLeft -= n;
if( nSrc==0 ){
nSrc = nData;
pSrc = pData;
}
}
releasePage(pToRelease);
return SQLITE_OK;
}
/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument so that MemPage.pParent holds the
** pointer in the third argument.
*/
static int reparentPage(BtShared *pBt, Pgno pgno, MemPage *pNewParent, int idx){
MemPage *pThis;
DbPage *pDbPage;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pNewParent!=0 );
if( pgno==0 ) return SQLITE_OK;
assert( pBt->pPager!=0 );
pDbPage = sqlite3PagerLookup(pBt->pPager, pgno);
if( pDbPage ){
pThis = (MemPage *)sqlite3PagerGetExtra(pDbPage);
if( pThis->isInit ){
assert( pThis->aData==sqlite3PagerGetData(pDbPage) );
if( pThis->pParent!=pNewParent ){
if( pThis->pParent ) sqlite3PagerUnref(pThis->pParent->pDbPage);
pThis->pParent = pNewParent;
sqlite3PagerRef(pNewParent->pDbPage);
}
pThis->idxParent = idx;
}
sqlite3PagerUnref(pDbPage);
}
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
return ptrmapPut(pBt, pgno, PTRMAP_BTREE, pNewParent->pgno);
}
#endif
return SQLITE_OK;
}
/*
** Change the pParent pointer of all children of pPage to point back
** to pPage.
**
** In other words, for every child of pPage, invoke reparentPage()
** to make sure that each child knows that pPage is its parent.
**
** This routine gets called after you memcpy() one page into
** another.
*/
static int reparentChildPages(MemPage *pPage){
int i;
BtShared *pBt = pPage->pBt;
int rc = SQLITE_OK;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
if( pPage->leaf ) return SQLITE_OK;
for(i=0; i<pPage->nCell; i++){
u8 *pCell = findCell(pPage, i);
if( !pPage->leaf ){
rc = reparentPage(pBt, get4byte(pCell), pPage, i);
if( rc!=SQLITE_OK ) return rc;
}
}
if( !pPage->leaf ){
rc = reparentPage(pBt, get4byte(&pPage->aData[pPage->hdrOffset+8]),
pPage, i);
pPage->idxShift = 0;
}
return rc;
}
/*
** Remove the i-th cell from pPage. This routine effects pPage only.
** The cell content is not freed or deallocated. It is assumed that
** the cell content has been copied someplace else. This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
*/
static void dropCell(MemPage *pPage, int idx, int sz){
int i; /* Loop counter */
int pc; /* Offset to cell content of cell being deleted */
u8 *data; /* pPage->aData */
u8 *ptr; /* Used to move bytes around within data[] */
assert( idx>=0 && idx<pPage->nCell );
assert( sz==cellSize(pPage, idx) );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
data = pPage->aData;
ptr = &data[pPage->cellOffset + 2*idx];
pc = get2byte(ptr);
assert( pc>10 && pc+sz<=pPage->pBt->usableSize );
freeSpace(pPage, pc, sz);
for(i=idx+1; i<pPage->nCell; i++, ptr+=2){
ptr[0] = ptr[2];
ptr[1] = ptr[3];
}
pPage->nCell--;
put2byte(&data[pPage->hdrOffset+3], pPage->nCell);
pPage->nFree += 2;
pPage->idxShift = 1;
}
/*
** Insert a new cell on pPage at cell index "i". pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there. If it
** will not fit, then make a copy of the cell content into pTemp if
** pTemp is not null. Regardless of pTemp, allocate a new entry
** in pPage->aOvfl[] and make it point to the cell content (either
** in pTemp or the original pCell) and also record its index.
** Allocating a new entry in pPage->aCell[] implies that
** pPage->nOverflow is incremented.
**
** If nSkip is non-zero, then do not copy the first nSkip bytes of the
** cell. The caller will overwrite them after this function returns. If
** nSkip is non-zero, then pCell may not point to an invalid memory location
** (but pCell+nSkip is always valid).
*/
static int insertCell(
MemPage *pPage, /* Page into which we are copying */
int i, /* New cell becomes the i-th cell of the page */
u8 *pCell, /* Content of the new cell */
int sz, /* Bytes of content in pCell */
u8 *pTemp, /* Temp storage space for pCell, if needed */
u8 nSkip /* Do not write the first nSkip bytes of the cell */
){
int idx; /* Where to write new cell content in data[] */
int j; /* Loop counter */
int top; /* First byte of content for any cell in data[] */
int end; /* First byte past the last cell pointer in data[] */
int ins; /* Index in data[] where new cell pointer is inserted */
int hdr; /* Offset into data[] of the page header */
int cellOffset; /* Address of first cell pointer in data[] */
u8 *data; /* The content of the whole page */
u8 *ptr; /* Used for moving information around in data[] */
assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
assert( sz==cellSizePtr(pPage, pCell) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
if( pPage->nOverflow || sz+2>pPage->nFree ){
if( pTemp ){
memcpy(pTemp+nSkip, pCell+nSkip, sz-nSkip);
pCell = pTemp;
}
j = pPage->nOverflow++;
assert( j<sizeof(pPage->aOvfl)/sizeof(pPage->aOvfl[0]) );
pPage->aOvfl[j].pCell = pCell;
pPage->aOvfl[j].idx = i;
pPage->nFree = 0;
}else{
int rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
data = pPage->aData;
hdr = pPage->hdrOffset;
top = get2byte(&data[hdr+5]);
cellOffset = pPage->cellOffset;
end = cellOffset + 2*pPage->nCell + 2;
ins = cellOffset + 2*i;
if( end > top - sz ){
rc = defragmentPage(pPage);
if( rc!=SQLITE_OK ) return rc;
top = get2byte(&data[hdr+5]);
assert( end + sz <= top );
}
idx = allocateSpace(pPage, sz);
assert( idx>0 );
assert( end <= get2byte(&data[hdr+5]) );
pPage->nCell++;
pPage->nFree -= 2;
memcpy(&data[idx+nSkip], pCell+nSkip, sz-nSkip);
for(j=end-2, ptr=&data[j]; j>ins; j-=2, ptr-=2){
ptr[0] = ptr[-2];
ptr[1] = ptr[-1];
}
put2byte(&data[ins], idx);
put2byte(&data[hdr+3], pPage->nCell);
pPage->idxShift = 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pPage->pBt->autoVacuum ){
/* The cell may contain a pointer to an overflow page. If so, write
** the entry for the overflow page into the pointer map.
*/
CellInfo info;
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
assert( (info.nData+(pPage->intKey?0:info.nKey))==info.nPayload );
if( (info.nData+(pPage->intKey?0:info.nKey))>info.nLocal ){
Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
rc = ptrmapPut(pPage->pBt, pgnoOvfl, PTRMAP_OVERFLOW1, pPage->pgno);
if( rc!=SQLITE_OK ) return rc;
}
}
#endif
}
return SQLITE_OK;
}
/*
** Add a list of cells to a page. The page should be initially empty.
** The cells are guaranteed to fit on the page.
*/
static void assemblePage(
MemPage *pPage, /* The page to be assemblied */
int nCell, /* The number of cells to add to this page */
u8 **apCell, /* Pointers to cell bodies */
int *aSize /* Sizes of the cells */
){
int i; /* Loop counter */
int totalSize; /* Total size of all cells */
int hdr; /* Index of page header */
int cellptr; /* Address of next cell pointer */
int cellbody; /* Address of next cell body */
u8 *data; /* Data for the page */
assert( pPage->nOverflow==0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
totalSize = 0;
for(i=0; i<nCell; i++){
totalSize += aSize[i];
}
assert( totalSize+2*nCell<=pPage->nFree );
assert( pPage->nCell==0 );
cellptr = pPage->cellOffset;
data = pPage->aData;
hdr = pPage->hdrOffset;
put2byte(&data[hdr+3], nCell);
if( nCell ){
cellbody = allocateSpace(pPage, totalSize);
assert( cellbody>0 );
assert( pPage->nFree >= 2*nCell );
pPage->nFree -= 2*nCell;
for(i=0; i<nCell; i++){
put2byte(&data[cellptr], cellbody);
memcpy(&data[cellbody], apCell[i], aSize[i]);
cellptr += 2;
cellbody += aSize[i];
}
assert( cellbody==pPage->pBt->usableSize );
}
pPage->nCell = nCell;
}
/*
** The following parameters determine how many adjacent pages get involved
** in a balancing operation. NN is the number of neighbors on either side
** of the page that participate in the balancing operation. NB is the
** total number of pages that participate, including the target page and
** NN neighbors on either side.
**
** The minimum value of NN is 1 (of course). Increasing NN above 1
** (to 2 or 3) gives a modest improvement in SELECT and DELETE performance
** in exchange for a larger degradation in INSERT and UPDATE performance.
** The value of NN appears to give the best results overall.
*/
#define NN 1 /* Number of neighbors on either side of pPage */
#define NB (NN*2+1) /* Total pages involved in the balance */
/* Forward reference */
static int balance(MemPage*, int);
#ifndef SQLITE_OMIT_QUICKBALANCE
/*
** This version of balance() handles the common special case where
** a new entry is being inserted on the extreme right-end of the
** tree, in other words, when the new entry will become the largest
** entry in the tree.
**
** Instead of trying balance the 3 right-most leaf pages, just add
** a new page to the right-hand side and put the one new entry in
** that page. This leaves the right side of the tree somewhat
** unbalanced. But odds are that we will be inserting new entries
** at the end soon afterwards so the nearly empty page will quickly
** fill up. On average.
**
** pPage is the leaf page which is the right-most page in the tree.
** pParent is its parent. pPage must have a single overflow entry
** which is also the right-most entry on the page.
*/
static int balance_quick(MemPage *pPage, MemPage *pParent){
int rc;
MemPage *pNew;
Pgno pgnoNew;
u8 *pCell;
int szCell;
CellInfo info;
BtShared *pBt = pPage->pBt;
int parentIdx = pParent->nCell; /* pParent new divider cell index */
int parentSize; /* Size of new divider cell */
u8 parentCell[64]; /* Space for the new divider cell */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
/* Allocate a new page. Insert the overflow cell from pPage
** into it. Then remove the overflow cell from pPage.
*/
rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
if( rc!=SQLITE_OK ){
return rc;
}
pCell = pPage->aOvfl[0].pCell;
szCell = cellSizePtr(pPage, pCell);
zeroPage(pNew, pPage->aData[0]);
assemblePage(pNew, 1, &pCell, &szCell);
pPage->nOverflow = 0;
/* Set the parent of the newly allocated page to pParent. */
pNew->pParent = pParent;
sqlite3PagerRef(pParent->pDbPage);
/* pPage is currently the right-child of pParent. Change this
** so that the right-child is the new page allocated above and
** pPage is the next-to-right child.
*/
assert( pPage->nCell>0 );
pCell = findCell(pPage, pPage->nCell-1);
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
rc = fillInCell(pParent, parentCell, 0, info.nKey, 0, 0, 0, &parentSize);
if( rc!=SQLITE_OK ){
return rc;
}
assert( parentSize<64 );
rc = insertCell(pParent, parentIdx, parentCell, parentSize, 0, 4);
if( rc!=SQLITE_OK ){
return rc;
}
put4byte(findOverflowCell(pParent,parentIdx), pPage->pgno);
put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If this is an auto-vacuum database, update the pointer map
** with entries for the new page, and any pointer from the
** cell on the page to an overflow page.
*/
if( pBt->autoVacuum ){
rc = ptrmapPut(pBt, pgnoNew, PTRMAP_BTREE, pParent->pgno);
if( rc==SQLITE_OK ){
rc = ptrmapPutOvfl(pNew, 0);
}
if( rc!=SQLITE_OK ){
releasePage(pNew);
return rc;
}
}
#endif
/* Release the reference to the new page and balance the parent page,
** in case the divider cell inserted caused it to become overfull.
*/
releasePage(pNew);
return balance(pParent, 0);
}
#endif /* SQLITE_OMIT_QUICKBALANCE */
/*
** This routine redistributes Cells on pPage and up to NN*2 siblings
** of pPage so that all pages have about the same amount of free space.
** Usually NN siblings on either side of pPage is used in the balancing,
** though more siblings might come from one side if pPage is the first
** or last child of its parent. If pPage has fewer than 2*NN siblings
** (something which can only happen if pPage is the root page or a
** child of root) then all available siblings participate in the balancing.
**
** The number of siblings of pPage might be increased or decreased by one or
** two in an effort to keep pages nearly full but not over full. The root page
** is special and is allowed to be nearly empty. If pPage is
** the root page, then the depth of the tree might be increased
** or decreased by one, as necessary, to keep the root page from being
** overfull or completely empty.
**
** Note that when this routine is called, some of the Cells on pPage
** might not actually be stored in pPage->aData[]. This can happen
** if the page is overfull. Part of the job of this routine is to
** make sure all Cells for pPage once again fit in pPage->aData[].
**
** In the course of balancing the siblings of pPage, the parent of pPage
** might become overfull or underfull. If that happens, then this routine
** is called recursively on the parent.
**
** If this routine fails for any reason, it might leave the database
** in a corrupted state. So if this routine fails, the database should
** be rolled back.
*/
static int balance_nonroot(MemPage *pPage){
MemPage *pParent; /* The parent of pPage */
BtShared *pBt; /* The whole database */
int nCell = 0; /* Number of cells in apCell[] */
int nMaxCells = 0; /* Allocated size of apCell, szCell, aFrom. */
int nOld; /* Number of pages in apOld[] */
int nNew; /* Number of pages in apNew[] */
int nDiv; /* Number of cells in apDiv[] */
int i, j, k; /* Loop counters */
int idx; /* Index of pPage in pParent->aCell[] */
int nxDiv; /* Next divider slot in pParent->aCell[] */
int rc; /* The return code */
int leafCorrection; /* 4 if pPage is a leaf. 0 if not */
int leafData; /* True if pPage is a leaf of a LEAFDATA tree */
int usableSpace; /* Bytes in pPage beyond the header */
int pageFlags; /* Value of pPage->aData[0] */
int subtotal; /* Subtotal of bytes in cells on one page */
int iSpace = 0; /* First unused byte of aSpace[] */
MemPage *apOld[NB]; /* pPage and up to two siblings */
Pgno pgnoOld[NB]; /* Page numbers for each page in apOld[] */
MemPage *apCopy[NB]; /* Private copies of apOld[] pages */
MemPage *apNew[NB+2]; /* pPage and up to NB siblings after balancing */
Pgno pgnoNew[NB+2]; /* Page numbers for each page in apNew[] */
u8 *apDiv[NB]; /* Divider cells in pParent */
int cntNew[NB+2]; /* Index in aCell[] of cell after i-th page */
int szNew[NB+2]; /* Combined size of cells place on i-th page */
u8 **apCell = 0; /* All cells begin balanced */
int *szCell; /* Local size of all cells in apCell[] */
u8 *aCopy[NB]; /* Space for holding data of apCopy[] */
u8 *aSpace; /* Space to hold copies of dividers cells */
#ifndef SQLITE_OMIT_AUTOVACUUM
u8 *aFrom = 0;
#endif
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
/*
** Find the parent page.
*/
assert( pPage->isInit );
assert( sqlite3PagerIswriteable(pPage->pDbPage) || pPage->nOverflow==1 );
pBt = pPage->pBt;
pParent = pPage->pParent;
assert( pParent );
if( SQLITE_OK!=(rc = sqlite3PagerWrite(pParent->pDbPage)) ){
return rc;
}
TRACE(("BALANCE: begin page %d child of %d\n", pPage->pgno, pParent->pgno));
#ifndef SQLITE_OMIT_QUICKBALANCE
/*
** A special case: If a new entry has just been inserted into a
** table (that is, a btree with integer keys and all data at the leaves)
** and the new entry is the right-most entry in the tree (it has the
** largest key) then use the special balance_quick() routine for
** balancing. balance_quick() is much faster and results in a tighter
** packing of data in the common case.
*/
if( pPage->leaf &&
pPage->intKey &&
pPage->leafData &&
pPage->nOverflow==1 &&
pPage->aOvfl[0].idx==pPage->nCell &&
pPage->pParent->pgno!=1 &&
get4byte(&pParent->aData[pParent->hdrOffset+8])==pPage->pgno
){
/*
** TODO: Check the siblings to the left of pPage. It may be that
** they are not full and no new page is required.
*/
return balance_quick(pPage, pParent);
}
#endif
if( SQLITE_OK!=(rc = sqlite3PagerWrite(pPage->pDbPage)) ){
return rc;
}
/*
** Find the cell in the parent page whose left child points back
** to pPage. The "idx" variable is the index of that cell. If pPage
** is the rightmost child of pParent then set idx to pParent->nCell
*/
if( pParent->idxShift ){
Pgno pgno;
pgno = pPage->pgno;
assert( pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
for(idx=0; idx<pParent->nCell; idx++){
if( get4byte(findCell(pParent, idx))==pgno ){
break;
}
}
assert( idx<pParent->nCell
|| get4byte(&pParent->aData[pParent->hdrOffset+8])==pgno );
}else{
idx = pPage->idxParent;
}
/*
** Initialize variables so that it will be safe to jump
** directly to balance_cleanup at any moment.
*/
nOld = nNew = 0;
sqlite3PagerRef(pParent->pDbPage);
/*
** Find sibling pages to pPage and the cells in pParent that divide
** the siblings. An attempt is made to find NN siblings on either
** side of pPage. More siblings are taken from one side, however, if
** pPage there are fewer than NN siblings on the other side. If pParent
** has NB or fewer children then all children of pParent are taken.
*/
nxDiv = idx - NN;
if( nxDiv + NB > pParent->nCell ){
nxDiv = pParent->nCell - NB + 1;
}
if( nxDiv<0 ){
nxDiv = 0;
}
nDiv = 0;
for(i=0, k=nxDiv; i<NB; i++, k++){
if( k<pParent->nCell ){
apDiv[i] = findCell(pParent, k);
nDiv++;
assert( !pParent->leaf );
pgnoOld[i] = get4byte(apDiv[i]);
}else if( k==pParent->nCell ){
pgnoOld[i] = get4byte(&pParent->aData[pParent->hdrOffset+8]);
}else{
break;
}
rc = getAndInitPage(pBt, pgnoOld[i], &apOld[i], pParent);
if( rc ) goto balance_cleanup;
apOld[i]->idxParent = k;
apCopy[i] = 0;
assert( i==nOld );
nOld++;
nMaxCells += 1+apOld[i]->nCell+apOld[i]->nOverflow;
}
/* Make nMaxCells a multiple of 2 in order to preserve 8-byte
** alignment */
nMaxCells = (nMaxCells + 1)&~1;
/*
** Allocate space for memory structures
*/
apCell = sqlite3_malloc(
nMaxCells*sizeof(u8*) /* apCell */
+ nMaxCells*sizeof(int) /* szCell */
+ ROUND8(sizeof(MemPage))*NB /* aCopy */
+ pBt->pageSize*(5+NB) /* aSpace */
+ (ISAUTOVACUUM ? nMaxCells : 0) /* aFrom */
);
if( apCell==0 ){
rc = SQLITE_NOMEM;
goto balance_cleanup;
}
szCell = (int*)&apCell[nMaxCells];
aCopy[0] = (u8*)&szCell[nMaxCells];
assert( ((aCopy[0] - (u8*)apCell) & 7)==0 ); /* 8-byte alignment required */
for(i=1; i<NB; i++){
aCopy[i] = &aCopy[i-1][pBt->pageSize+ROUND8(sizeof(MemPage))];
assert( ((aCopy[i] - (u8*)apCell) & 7)==0 ); /* 8-byte alignment required */
}
aSpace = &aCopy[NB-1][pBt->pageSize+ROUND8(sizeof(MemPage))];
assert( ((aSpace - (u8*)apCell) & 7)==0 ); /* 8-byte alignment required */
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
aFrom = &aSpace[5*pBt->pageSize];
}
#endif
/*
** Make copies of the content of pPage and its siblings into aOld[].
** The rest of this function will use data from the copies rather
** that the original pages since the original pages will be in the
** process of being overwritten.
*/
for(i=0; i<nOld; i++){
MemPage *p = apCopy[i] = (MemPage*)aCopy[i];
memcpy(p, apOld[i], sizeof(MemPage));
p->aData = (void*)&p[1];
memcpy(p->aData, apOld[i]->aData, pBt->pageSize);
}
/*
** Load pointers to all cells on sibling pages and the divider cells
** into the local apCell[] array. Make copies of the divider cells
** into space obtained form aSpace[] and remove the the divider Cells
** from pParent.
**
** If the siblings are on leaf pages, then the child pointers of the
** divider cells are stripped from the cells before they are copied
** into aSpace[]. In this way, all cells in apCell[] are without
** child pointers. If siblings are not leaves, then all cell in
** apCell[] include child pointers. Either way, all cells in apCell[]
** are alike.
**
** leafCorrection: 4 if pPage is a leaf. 0 if pPage is not a leaf.
** leafData: 1 if pPage holds key+data and pParent holds only keys.
*/
nCell = 0;
leafCorrection = pPage->leaf*4;
leafData = pPage->leafData && pPage->leaf;
for(i=0; i<nOld; i++){
MemPage *pOld = apCopy[i];
int limit = pOld->nCell+pOld->nOverflow;
for(j=0; j<limit; j++){
assert( nCell<nMaxCells );
apCell[nCell] = findOverflowCell(pOld, j);
szCell[nCell] = cellSizePtr(pOld, apCell[nCell]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
int a;
aFrom[nCell] = i;
for(a=0; a<pOld->nOverflow; a++){
if( pOld->aOvfl[a].pCell==apCell[nCell] ){
aFrom[nCell] = 0xFF;
break;
}
}
}
#endif
nCell++;
}
if( i<nOld-1 ){
int sz = cellSizePtr(pParent, apDiv[i]);
if( leafData ){
/* With the LEAFDATA flag, pParent cells hold only INTKEYs that
** are duplicates of keys on the child pages. We need to remove
** the divider cells from pParent, but the dividers cells are not
** added to apCell[] because they are duplicates of child cells.
*/
dropCell(pParent, nxDiv, sz);
}else{
u8 *pTemp;
assert( nCell<nMaxCells );
szCell[nCell] = sz;
pTemp = &aSpace[iSpace];
iSpace += sz;
assert( iSpace<=pBt->pageSize*5 );
memcpy(pTemp, apDiv[i], sz);
apCell[nCell] = pTemp+leafCorrection;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
aFrom[nCell] = 0xFF;
}
#endif
dropCell(pParent, nxDiv, sz);
szCell[nCell] -= leafCorrection;
assert( get4byte(pTemp)==pgnoOld[i] );
if( !pOld->leaf ){
assert( leafCorrection==0 );
/* The right pointer of the child page pOld becomes the left
** pointer of the divider cell */
memcpy(apCell[nCell], &pOld->aData[pOld->hdrOffset+8], 4);
}else{
assert( leafCorrection==4 );
if( szCell[nCell]<4 ){
/* Do not allow any cells smaller than 4 bytes. */
szCell[nCell] = 4;
}
}
nCell++;
}
}
}
/*
** Figure out the number of pages needed to hold all nCell cells.
** Store this number in "k". Also compute szNew[] which is the total
** size of all cells on the i-th page and cntNew[] which is the index
** in apCell[] of the cell that divides page i from page i+1.
** cntNew[k] should equal nCell.
**
** Values computed by this block:
**
** k: The total number of sibling pages
** szNew[i]: Spaced used on the i-th sibling page.
** cntNew[i]: Index in apCell[] and szCell[] for the first cell to
** the right of the i-th sibling page.
** usableSpace: Number of bytes of space available on each sibling.
**
*/
usableSpace = pBt->usableSize - 12 + leafCorrection;
for(subtotal=k=i=0; i<nCell; i++){
assert( i<nMaxCells );
subtotal += szCell[i] + 2;
if( subtotal > usableSpace ){
szNew[k] = subtotal - szCell[i];
cntNew[k] = i;
if( leafData ){ i--; }
subtotal = 0;
k++;
}
}
szNew[k] = subtotal;
cntNew[k] = nCell;
k++;
/*
** The packing computed by the previous block is biased toward the siblings
** on the left side. The left siblings are always nearly full, while the
** right-most sibling might be nearly empty. This block of code attempts
** to adjust the packing of siblings to get a better balance.
**
** This adjustment is more than an optimization. The packing above might
** be so out of balance as to be illegal. For example, the right-most
** sibling might be completely empty. This adjustment is not optional.
*/
for(i=k-1; i>0; i--){
int szRight = szNew[i]; /* Size of sibling on the right */
int szLeft = szNew[i-1]; /* Size of sibling on the left */
int r; /* Index of right-most cell in left sibling */
int d; /* Index of first cell to the left of right sibling */
r = cntNew[i-1] - 1;
d = r + 1 - leafData;
assert( d<nMaxCells );
assert( r<nMaxCells );
while( szRight==0 || szRight+szCell[d]+2<=szLeft-(szCell[r]+2) ){
szRight += szCell[d] + 2;
szLeft -= szCell[r] + 2;
cntNew[i-1]--;
r = cntNew[i-1] - 1;
d = r + 1 - leafData;
}
szNew[i] = szRight;
szNew[i-1] = szLeft;
}
/* Either we found one or more cells (cntnew[0])>0) or we are the
** a virtual root page. A virtual root page is when the real root
** page is page 1 and we are the only child of that page.
*/
assert( cntNew[0]>0 || (pParent->pgno==1 && pParent->nCell==0) );
/*
** Allocate k new pages. Reuse old pages where possible.
*/
assert( pPage->pgno>1 );
pageFlags = pPage->aData[0];
for(i=0; i<k; i++){
MemPage *pNew;
if( i<nOld ){
pNew = apNew[i] = apOld[i];
pgnoNew[i] = pgnoOld[i];
apOld[i] = 0;
rc = sqlite3PagerWrite(pNew->pDbPage);
nNew++;
if( rc ) goto balance_cleanup;
}else{
assert( i>0 );
rc = allocateBtreePage(pBt, &pNew, &pgnoNew[i], pgnoNew[i-1], 0);
if( rc ) goto balance_cleanup;
apNew[i] = pNew;
nNew++;
}
zeroPage(pNew, pageFlags);
}
/* Free any old pages that were not reused as new pages.
*/
while( i<nOld ){
rc = freePage(apOld[i]);
if( rc ) goto balance_cleanup;
releasePage(apOld[i]);
apOld[i] = 0;
i++;
}
/*
** Put the new pages in accending order. This helps to
** keep entries in the disk file in order so that a scan
** of the table is a linear scan through the file. That
** in turn helps the operating system to deliver pages
** from the disk more rapidly.
**
** An O(n^2) insertion sort algorithm is used, but since
** n is never more than NB (a small constant), that should
** not be a problem.
**
** When NB==3, this one optimization makes the database
** about 25% faster for large insertions and deletions.
*/
for(i=0; i<k-1; i++){
int minV = pgnoNew[i];
int minI = i;
for(j=i+1; j<k; j++){
if( pgnoNew[j]<(unsigned)minV ){
minI = j;
minV = pgnoNew[j];
}
}
if( minI>i ){
int t;
MemPage *pT;
t = pgnoNew[i];
pT = apNew[i];
pgnoNew[i] = pgnoNew[minI];
apNew[i] = apNew[minI];
pgnoNew[minI] = t;
apNew[minI] = pT;
}
}
TRACE(("BALANCE: old: %d %d %d new: %d(%d) %d(%d) %d(%d) %d(%d) %d(%d)\n",
pgnoOld[0],
nOld>=2 ? pgnoOld[1] : 0,
nOld>=3 ? pgnoOld[2] : 0,
pgnoNew[0], szNew[0],
nNew>=2 ? pgnoNew[1] : 0, nNew>=2 ? szNew[1] : 0,
nNew>=3 ? pgnoNew[2] : 0, nNew>=3 ? szNew[2] : 0,
nNew>=4 ? pgnoNew[3] : 0, nNew>=4 ? szNew[3] : 0,
nNew>=5 ? pgnoNew[4] : 0, nNew>=5 ? szNew[4] : 0));
/*
** Evenly distribute the data in apCell[] across the new pages.
** Insert divider cells into pParent as necessary.
*/
j = 0;
for(i=0; i<nNew; i++){
/* Assemble the new sibling page. */
MemPage *pNew = apNew[i];
assert( j<nMaxCells );
assert( pNew->pgno==pgnoNew[i] );
assemblePage(pNew, cntNew[i]-j, &apCell[j], &szCell[j]);
assert( pNew->nCell>0 || (nNew==1 && cntNew[0]==0) );
assert( pNew->nOverflow==0 );
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If this is an auto-vacuum database, update the pointer map entries
** that point to the siblings that were rearranged. These can be: left
** children of cells, the right-child of the page, or overflow pages
** pointed to by cells.
*/
if( pBt->autoVacuum ){
for(k=j; k<cntNew[i]; k++){
assert( k<nMaxCells );
if( aFrom[k]==0xFF || apCopy[aFrom[k]]->pgno!=pNew->pgno ){
rc = ptrmapPutOvfl(pNew, k-j);
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
}
}
#endif
j = cntNew[i];
/* If the sibling page assembled above was not the right-most sibling,
** insert a divider cell into the parent page.
*/
if( i<nNew-1 && j<nCell ){
u8 *pCell;
u8 *pTemp;
int sz;
assert( j<nMaxCells );
pCell = apCell[j];
sz = szCell[j] + leafCorrection;
if( !pNew->leaf ){
memcpy(&pNew->aData[8], pCell, 4);
pTemp = 0;
}else if( leafData ){
/* If the tree is a leaf-data tree, and the siblings are leaves,
** then there is no divider cell in apCell[]. Instead, the divider
** cell consists of the integer key for the right-most cell of
** the sibling-page assembled above only.
*/
CellInfo info;
j--;
sqlite3BtreeParseCellPtr(pNew, apCell[j], &info);
pCell = &aSpace[iSpace];
fillInCell(pParent, pCell, 0, info.nKey, 0, 0, 0, &sz);
iSpace += sz;
assert( iSpace<=pBt->pageSize*5 );
pTemp = 0;
}else{
pCell -= 4;
pTemp = &aSpace[iSpace];
iSpace += sz;
assert( iSpace<=pBt->pageSize*5 );
/* Obscure case for non-leaf-data trees: If the cell at pCell was
** previously stored on a leaf node, and it's reported size was 4
** bytes, then it may actually be smaller than this
** (see sqlite3BtreeParseCellPtr(), 4 bytes is the minimum size of
** any cell). But it's important to pass the correct size to
** insertCell(), so reparse the cell now.
**
** Note that this can never happen in an SQLite data file, as all
** cells are at least 4 bytes. It only happens in b-trees used
** to evaluate "IN (SELECT ...)" and similar clauses.
*/
if( szCell[j]==4 ){
assert(leafCorrection==4);
sz = cellSizePtr(pParent, pCell);
}
}
rc = insertCell(pParent, nxDiv, pCell, sz, pTemp, 4);
if( rc!=SQLITE_OK ) goto balance_cleanup;
put4byte(findOverflowCell(pParent,nxDiv), pNew->pgno);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If this is an auto-vacuum database, and not a leaf-data tree,
** then update the pointer map with an entry for the overflow page
** that the cell just inserted points to (if any).
*/
if( pBt->autoVacuum && !leafData ){
rc = ptrmapPutOvfl(pParent, nxDiv);
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
#endif
j++;
nxDiv++;
}
}
assert( j==nCell );
assert( nOld>0 );
assert( nNew>0 );
if( (pageFlags & PTF_LEAF)==0 ){
memcpy(&apNew[nNew-1]->aData[8], &apCopy[nOld-1]->aData[8], 4);
}
if( nxDiv==pParent->nCell+pParent->nOverflow ){
/* Right-most sibling is the right-most child of pParent */
put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew[nNew-1]);
}else{
/* Right-most sibling is the left child of the first entry in pParent
** past the right-most divider entry */
put4byte(findOverflowCell(pParent, nxDiv), pgnoNew[nNew-1]);
}
/*
** Reparent children of all cells.
*/
for(i=0; i<nNew; i++){
rc = reparentChildPages(apNew[i]);
if( rc!=SQLITE_OK ) goto balance_cleanup;
}
rc = reparentChildPages(pParent);
if( rc!=SQLITE_OK ) goto balance_cleanup;
/*
** Balance the parent page. Note that the current page (pPage) might
** have been added to the freelist so it might no longer be initialized.
** But the parent page will always be initialized.
*/
assert( pParent->isInit );
rc = balance(pParent, 0);
/*
** Cleanup before returning.
*/
balance_cleanup:
sqlite3_free(apCell);
for(i=0; i<nOld; i++){
releasePage(apOld[i]);
}
for(i=0; i<nNew; i++){
releasePage(apNew[i]);
}
releasePage(pParent);
TRACE(("BALANCE: finished with %d: old=%d new=%d cells=%d\n",
pPage->pgno, nOld, nNew, nCell));
return rc;
}
/*
** This routine is called for the root page of a btree when the root
** page contains no cells. This is an opportunity to make the tree
** shallower by one level.
*/
static int balance_shallower(MemPage *pPage){
MemPage *pChild; /* The only child page of pPage */
Pgno pgnoChild; /* Page number for pChild */
int rc = SQLITE_OK; /* Return code from subprocedures */
BtShared *pBt; /* The main BTree structure */
int mxCellPerPage; /* Maximum number of cells per page */
u8 **apCell; /* All cells from pages being balanced */
int *szCell; /* Local size of all cells */
assert( pPage->pParent==0 );
assert( pPage->nCell==0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pBt = pPage->pBt;
mxCellPerPage = MX_CELL(pBt);
apCell = sqlite3_malloc( mxCellPerPage*(sizeof(u8*)+sizeof(int)) );
if( apCell==0 ) return SQLITE_NOMEM;
szCell = (int*)&apCell[mxCellPerPage];
if( pPage->leaf ){
/* The table is completely empty */
TRACE(("BALANCE: empty table %d\n", pPage->pgno));
}else{
/* The root page is empty but has one child. Transfer the
** information from that one child into the root page if it
** will fit. This reduces the depth of the tree by one.
**
** If the root page is page 1, it has less space available than
** its child (due to the 100 byte header that occurs at the beginning
** of the database fle), so it might not be able to hold all of the
** information currently contained in the child. If this is the
** case, then do not do the transfer. Leave page 1 empty except
** for the right-pointer to the child page. The child page becomes
** the virtual root of the tree.
*/
pgnoChild = get4byte(&pPage->aData[pPage->hdrOffset+8]);
assert( pgnoChild>0 );
assert( pgnoChild<=sqlite3PagerPagecount(pPage->pBt->pPager) );
rc = sqlite3BtreeGetPage(pPage->pBt, pgnoChild, &pChild, 0);
if( rc ) goto end_shallow_balance;
if( pPage->pgno==1 ){
rc = sqlite3BtreeInitPage(pChild, pPage);
if( rc ) goto end_shallow_balance;
assert( pChild->nOverflow==0 );
if( pChild->nFree>=100 ){
/* The child information will fit on the root page, so do the
** copy */
int i;
zeroPage(pPage, pChild->aData[0]);
for(i=0; i<pChild->nCell; i++){
apCell[i] = findCell(pChild,i);
szCell[i] = cellSizePtr(pChild, apCell[i]);
}
assemblePage(pPage, pChild->nCell, apCell, szCell);
/* Copy the right-pointer of the child to the parent. */
put4byte(&pPage->aData[pPage->hdrOffset+8],
get4byte(&pChild->aData[pChild->hdrOffset+8]));
freePage(pChild);
TRACE(("BALANCE: child %d transfer to page 1\n", pChild->pgno));
}else{
/* The child has more information that will fit on the root.
** The tree is already balanced. Do nothing. */
TRACE(("BALANCE: child %d will not fit on page 1\n", pChild->pgno));
}
}else{
memcpy(pPage->aData, pChild->aData, pPage->pBt->usableSize);
pPage->isInit = 0;
pPage->pParent = 0;
rc = sqlite3BtreeInitPage(pPage, 0);
assert( rc==SQLITE_OK );
freePage(pChild);
TRACE(("BALANCE: transfer child %d into root %d\n",
pChild->pgno, pPage->pgno));
}
rc = reparentChildPages(pPage);
assert( pPage->nOverflow==0 );
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
int i;
for(i=0; i<pPage->nCell; i++){
rc = ptrmapPutOvfl(pPage, i);
if( rc!=SQLITE_OK ){
goto end_shallow_balance;
}
}
}
#endif
releasePage(pChild);
}
end_shallow_balance:
sqlite3_free(apCell);
return rc;
}
/*
** The root page is overfull
**
** When this happens, Create a new child page and copy the
** contents of the root into the child. Then make the root
** page an empty page with rightChild pointing to the new
** child. Finally, call balance_internal() on the new child
** to cause it to split.
*/
static int balance_deeper(MemPage *pPage){
int rc; /* Return value from subprocedures */
MemPage *pChild; /* Pointer to a new child page */
Pgno pgnoChild; /* Page number of the new child page */
BtShared *pBt; /* The BTree */
int usableSize; /* Total usable size of a page */
u8 *data; /* Content of the parent page */
u8 *cdata; /* Content of the child page */
int hdr; /* Offset to page header in parent */
int brk; /* Offset to content of first cell in parent */
assert( pPage->pParent==0 );
assert( pPage->nOverflow>0 );
pBt = pPage->pBt;
assert( sqlite3_mutex_held(pBt->mutex) );
rc = allocateBtreePage(pBt, &pChild, &pgnoChild, pPage->pgno, 0);
if( rc ) return rc;
assert( sqlite3PagerIswriteable(pChild->pDbPage) );
usableSize = pBt->usableSize;
data = pPage->aData;
hdr = pPage->hdrOffset;
brk = get2byte(&data[hdr+5]);
cdata = pChild->aData;
memcpy(cdata, &data[hdr], pPage->cellOffset+2*pPage->nCell-hdr);
memcpy(&cdata[brk], &data[brk], usableSize-brk);
assert( pChild->isInit==0 );
rc = sqlite3BtreeInitPage(pChild, pPage);
if( rc ) goto balancedeeper_out;
memcpy(pChild->aOvfl, pPage->aOvfl, pPage->nOverflow*sizeof(pPage->aOvfl[0]));
pChild->nOverflow = pPage->nOverflow;
if( pChild->nOverflow ){
pChild->nFree = 0;
}
assert( pChild->nCell==pPage->nCell );
zeroPage(pPage, pChild->aData[0] & ~PTF_LEAF);
put4byte(&pPage->aData[pPage->hdrOffset+8], pgnoChild);
TRACE(("BALANCE: copy root %d into %d\n", pPage->pgno, pChild->pgno));
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
int i;
rc = ptrmapPut(pBt, pChild->pgno, PTRMAP_BTREE, pPage->pgno);
if( rc ) goto balancedeeper_out;
for(i=0; i<pChild->nCell; i++){
rc = ptrmapPutOvfl(pChild, i);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
#endif
rc = balance_nonroot(pChild);
balancedeeper_out:
releasePage(pChild);
return rc;
}
/*
** Decide if the page pPage needs to be balanced. If balancing is
** required, call the appropriate balancing routine.
*/
static int balance(MemPage *pPage, int insert){
int rc = SQLITE_OK;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
if( pPage->pParent==0 ){
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc==SQLITE_OK && pPage->nOverflow>0 ){
rc = balance_deeper(pPage);
}
if( rc==SQLITE_OK && pPage->nCell==0 ){
rc = balance_shallower(pPage);
}
}else{
if( pPage->nOverflow>0 ||
(!insert && pPage->nFree>pPage->pBt->usableSize*2/3) ){
rc = balance_nonroot(pPage);
}
}
return rc;
}
/*
** This routine checks all cursors that point to table pgnoRoot.
** If any of those cursors were opened with wrFlag==0 in a different
** database connection (a database connection that shares the pager
** cache with the current connection) and that other connection
** is not in the ReadUncommmitted state, then this routine returns
** SQLITE_LOCKED.
**
** In addition to checking for read-locks (where a read-lock
** means a cursor opened with wrFlag==0) this routine also moves
** all write cursors so that they are pointing to the
** first Cell on the root page. This is necessary because an insert
** or delete might change the number of cells on a page or delete
** a page entirely and we do not want to leave any cursors
** pointing to non-existant pages or cells.
*/
static int checkReadLocks(Btree *pBtree, Pgno pgnoRoot, BtCursor *pExclude){
BtCursor *p;
BtShared *pBt = pBtree->pBt;
sqlite3 *db = pBtree->pSqlite;
assert( sqlite3BtreeHoldsMutex(pBtree) );
for(p=pBt->pCursor; p; p=p->pNext){
if( p==pExclude ) continue;
if( p->eState!=CURSOR_VALID ) continue;
if( p->pgnoRoot!=pgnoRoot ) continue;
if( p->wrFlag==0 ){
sqlite3 *dbOther = p->pBtree->pSqlite;
if( dbOther==0 ||
(dbOther!=db && (dbOther->flags & SQLITE_ReadUncommitted)==0) ){
return SQLITE_LOCKED;
}
}else if( p->pPage->pgno!=p->pgnoRoot ){
moveToRoot(p);
}
}
return SQLITE_OK;
}
/*
** Insert a new record into the BTree. The key is given by (pKey,nKey)
** and the data is given by (pData,nData). The cursor is used only to
** define what table the record should be inserted into. The cursor
** is left pointing at a random location.
**
** For an INTKEY table, only the nKey value of the key is used. pKey is
** ignored. For a ZERODATA table, the pData and nData are both ignored.
*/
int sqlite3BtreeInsert(
BtCursor *pCur, /* Insert data into the table of this cursor */
const void *pKey, i64 nKey, /* The key of the new record */
const void *pData, int nData, /* The data of the new record */
int nZero, /* Number of extra 0 bytes to append to data */
int appendBias /* True if this is likely an append */
){
int rc;
int loc;
int szNew;
MemPage *pPage;
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
unsigned char *oldCell;
unsigned char *newCell = 0;
assert( cursorHoldsMutex(pCur) );
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction before doing an insert */
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
return rc;
}
assert( !pBt->readOnly );
if( !pCur->wrFlag ){
return SQLITE_PERM; /* Cursor not open for writing */
}
if( checkReadLocks(pCur->pBtree, pCur->pgnoRoot, pCur) ){
return SQLITE_LOCKED; /* The table pCur points to has a read lock */
}
if( pCur->eState==CURSOR_FAULT ){
return pCur->skip;
}
/* Save the positions of any other cursors open on this table */
clearCursorPosition(pCur);
if(
SQLITE_OK!=(rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur)) ||
SQLITE_OK!=(rc = sqlite3BtreeMoveto(pCur, pKey, nKey, appendBias, &loc))
){
return rc;
}
pPage = pCur->pPage;
assert( pPage->intKey || nKey>=0 );
assert( pPage->leaf || !pPage->leafData );
TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
pCur->pgnoRoot, nKey, nData, pPage->pgno,
loc==0 ? "overwrite" : "new entry"));
assert( pPage->isInit );
newCell = sqlite3_malloc( MX_CELL_SIZE(pBt) );
if( newCell==0 ) return SQLITE_NOMEM;
rc = fillInCell(pPage, newCell, pKey, nKey, pData, nData, nZero, &szNew);
if( rc ) goto end_insert;
assert( szNew==cellSizePtr(pPage, newCell) );
assert( szNew<=MX_CELL_SIZE(pBt) );
if( loc==0 && CURSOR_VALID==pCur->eState ){
int szOld;
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ){
goto end_insert;
}
oldCell = findCell(pPage, pCur->idx);
if( !pPage->leaf ){
memcpy(newCell, oldCell, 4);
}
szOld = cellSizePtr(pPage, oldCell);
rc = clearCell(pPage, oldCell);
if( rc ) goto end_insert;
dropCell(pPage, pCur->idx, szOld);
}else if( loc<0 && pPage->nCell>0 ){
assert( pPage->leaf );
pCur->idx++;
pCur->info.nSize = 0;
}else{
assert( pPage->leaf );
}
rc = insertCell(pPage, pCur->idx, newCell, szNew, 0, 0);
if( rc!=SQLITE_OK ) goto end_insert;
rc = balance(pPage, 1);
/* sqlite3BtreePageDump(pCur->pBt, pCur->pgnoRoot, 1); */
/* fflush(stdout); */
if( rc==SQLITE_OK ){
moveToRoot(pCur);
}
end_insert:
sqlite3_free(newCell);
return rc;
}
/*
** Delete the entry that the cursor is pointing to. The cursor
** is left pointing at a random location.
*/
int sqlite3BtreeDelete(BtCursor *pCur){
MemPage *pPage = pCur->pPage;
unsigned char *pCell;
int rc;
Pgno pgnoChild = 0;
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
assert( cursorHoldsMutex(pCur) );
assert( pPage->isInit );
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction before doing a delete */
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
return rc;
}
assert( !pBt->readOnly );
if( pCur->eState==CURSOR_FAULT ){
return pCur->skip;
}
if( pCur->idx >= pPage->nCell ){
return SQLITE_ERROR; /* The cursor is not pointing to anything */
}
if( !pCur->wrFlag ){
return SQLITE_PERM; /* Did not open this cursor for writing */
}
if( checkReadLocks(pCur->pBtree, pCur->pgnoRoot, pCur) ){
return SQLITE_LOCKED; /* The table pCur points to has a read lock */
}
/* Restore the current cursor position (a no-op if the cursor is not in
** CURSOR_REQUIRESEEK state) and save the positions of any other cursors
** open on the same table. Then call sqlite3PagerWrite() on the page
** that the entry will be deleted from.
*/
if(
(rc = restoreOrClearCursorPosition(pCur))!=0 ||
(rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur))!=0 ||
(rc = sqlite3PagerWrite(pPage->pDbPage))!=0
){
return rc;
}
/* Locate the cell within it's page and leave pCell pointing to the
** data. The clearCell() call frees any overflow pages associated with the
** cell. The cell itself is still intact.
*/
pCell = findCell(pPage, pCur->idx);
if( !pPage->leaf ){
pgnoChild = get4byte(pCell);
}
rc = clearCell(pPage, pCell);
if( rc ){
return rc;
}
if( !pPage->leaf ){
/*
** The entry we are about to delete is not a leaf so if we do not
** do something we will leave a hole on an internal page.
** We have to fill the hole by moving in a cell from a leaf. The
** next Cell after the one to be deleted is guaranteed to exist and
** to be a leaf so we can use it.
*/
BtCursor leafCur;
unsigned char *pNext;
int szNext; /* The compiler warning is wrong: szNext is always
** initialized before use. Adding an extra initialization
** to silence the compiler slows down the code. */
int notUsed;
unsigned char *tempCell = 0;
assert( !pPage->leafData );
sqlite3BtreeGetTempCursor(pCur, &leafCur);
rc = sqlite3BtreeNext(&leafCur, &notUsed);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(leafCur.pPage->pDbPage);
}
if( rc==SQLITE_OK ){
TRACE(("DELETE: table=%d delete internal from %d replace from leaf %d\n",
pCur->pgnoRoot, pPage->pgno, leafCur.pPage->pgno));
dropCell(pPage, pCur->idx, cellSizePtr(pPage, pCell));
pNext = findCell(leafCur.pPage, leafCur.idx);
szNext = cellSizePtr(leafCur.pPage, pNext);
assert( MX_CELL_SIZE(pBt)>=szNext+4 );
tempCell = sqlite3_malloc( MX_CELL_SIZE(pBt) );
if( tempCell==0 ){
rc = SQLITE_NOMEM;
}
}
if( rc==SQLITE_OK ){
rc = insertCell(pPage, pCur->idx, pNext-4, szNext+4, tempCell, 0);
}
if( rc==SQLITE_OK ){
put4byte(findOverflowCell(pPage, pCur->idx), pgnoChild);
rc = balance(pPage, 0);
}
if( rc==SQLITE_OK ){
dropCell(leafCur.pPage, leafCur.idx, szNext);
rc = balance(leafCur.pPage, 0);
}
sqlite3_free(tempCell);
sqlite3BtreeReleaseTempCursor(&leafCur);
}else{
TRACE(("DELETE: table=%d delete from leaf %d\n",
pCur->pgnoRoot, pPage->pgno));
dropCell(pPage, pCur->idx, cellSizePtr(pPage, pCell));
rc = balance(pPage, 0);
}
if( rc==SQLITE_OK ){
moveToRoot(pCur);
}
return rc;
}
/*
** Create a new BTree table. Write into *piTable the page
** number for the root page of the new table.
**
** The type of type is determined by the flags parameter. Only the
** following values of flags are currently in use. Other values for
** flags might not work:
**
** BTREE_INTKEY|BTREE_LEAFDATA Used for SQL tables with rowid keys
** BTREE_ZERODATA Used for SQL indices
*/
static int btreeCreateTable(Btree *p, int *piTable, int flags){
BtShared *pBt = p->pBt;
MemPage *pRoot;
Pgno pgnoRoot;
int rc;
assert( sqlite3BtreeHoldsMutex(p) );
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction first */
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
return rc;
}
assert( !pBt->readOnly );
#ifdef SQLITE_OMIT_AUTOVACUUM
rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
if( rc ){
return rc;
}
#else
if( pBt->autoVacuum ){
Pgno pgnoMove; /* Move a page here to make room for the root-page */
MemPage *pPageMove; /* The page to move to. */
/* Creating a new table may probably require moving an existing database
** to make room for the new tables root page. In case this page turns
** out to be an overflow page, delete all overflow page-map caches
** held by open cursors.
*/
invalidateAllOverflowCache(pBt);
/* Read the value of meta[3] from the database to determine where the
** root page of the new table should go. meta[3] is the largest root-page
** created so far, so the new root-page is (meta[3]+1).
*/
rc = sqlite3BtreeGetMeta(p, 4, &pgnoRoot);
if( rc!=SQLITE_OK ){
return rc;
}
pgnoRoot++;
/* The new root-page may not be allocated on a pointer-map page, or the
** PENDING_BYTE page.
*/
if( pgnoRoot==PTRMAP_PAGENO(pBt, pgnoRoot) ||
pgnoRoot==PENDING_BYTE_PAGE(pBt) ){
pgnoRoot++;
}
assert( pgnoRoot>=3 );
/* Allocate a page. The page that currently resides at pgnoRoot will
** be moved to the allocated page (unless the allocated page happens
** to reside at pgnoRoot).
*/
rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, 1);
if( rc!=SQLITE_OK ){
return rc;
}
if( pgnoMove!=pgnoRoot ){
/* pgnoRoot is the page that will be used for the root-page of
** the new table (assuming an error did not occur). But we were
** allocated pgnoMove. If required (i.e. if it was not allocated
** by extending the file), the current page at position pgnoMove
** is already journaled.
*/
u8 eType;
Pgno iPtrPage;
releasePage(pPageMove);
/* Move the page currently at pgnoRoot to pgnoMove. */
rc = sqlite3BtreeGetPage(pBt, pgnoRoot, &pRoot, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = ptrmapGet(pBt, pgnoRoot, &eType, &iPtrPage);
if( rc!=SQLITE_OK || eType==PTRMAP_ROOTPAGE || eType==PTRMAP_FREEPAGE ){
releasePage(pRoot);
return rc;
}
assert( eType!=PTRMAP_ROOTPAGE );
assert( eType!=PTRMAP_FREEPAGE );
rc = sqlite3PagerWrite(pRoot->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pRoot);
return rc;
}
rc = relocatePage(pBt, pRoot, eType, iPtrPage, pgnoMove);
releasePage(pRoot);
/* Obtain the page at pgnoRoot */
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3BtreeGetPage(pBt, pgnoRoot, &pRoot, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pRoot->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pRoot);
return rc;
}
}else{
pRoot = pPageMove;
}
/* Update the pointer-map and meta-data with the new root-page number. */
rc = ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0);
if( rc ){
releasePage(pRoot);
return rc;
}
rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
if( rc ){
releasePage(pRoot);
return rc;
}
}else{
rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
if( rc ) return rc;
}
#endif
assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
zeroPage(pRoot, flags | PTF_LEAF);
sqlite3PagerUnref(pRoot->pDbPage);
*piTable = (int)pgnoRoot;
return SQLITE_OK;
}
int sqlite3BtreeCreateTable(Btree *p, int *piTable, int flags){
int rc;
sqlite3BtreeEnter(p);
rc = btreeCreateTable(p, piTable, flags);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Erase the given database page and all its children. Return
** the page to the freelist.
*/
static int clearDatabasePage(
BtShared *pBt, /* The BTree that contains the table */
Pgno pgno, /* Page number to clear */
MemPage *pParent, /* Parent page. NULL for the root */
int freePageFlag /* Deallocate page if true */
){
MemPage *pPage = 0;
int rc;
unsigned char *pCell;
int i;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pgno>sqlite3PagerPagecount(pBt->pPager) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getAndInitPage(pBt, pgno, &pPage, pParent);
if( rc ) goto cleardatabasepage_out;
for(i=0; i<pPage->nCell; i++){
pCell = findCell(pPage, i);
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(pCell), pPage->pParent, 1);
if( rc ) goto cleardatabasepage_out;
}
rc = clearCell(pPage, pCell);
if( rc ) goto cleardatabasepage_out;
}
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(&pPage->aData[8]), pPage->pParent, 1);
if( rc ) goto cleardatabasepage_out;
}
if( freePageFlag ){
rc = freePage(pPage);
}else if( (rc = sqlite3PagerWrite(pPage->pDbPage))==0 ){
zeroPage(pPage, pPage->aData[0] | PTF_LEAF);
}
cleardatabasepage_out:
releasePage(pPage);
return rc;
}
/*
** Delete all information from a single table in the database. iTable is
** the page number of the root of the table. After this routine returns,
** the root page is empty, but still exists.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** read cursors on the table. Open write cursors are moved to the
** root of the table.
*/
int sqlite3BtreeClearTable(Btree *p, int iTable){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( p->inTrans!=TRANS_WRITE ){
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}else if( (rc = checkReadLocks(p, iTable, 0))!=SQLITE_OK ){
/* nothing to do */
}else if( SQLITE_OK!=(rc = saveAllCursors(pBt, iTable, 0)) ){
/* nothing to do */
}else{
rc = clearDatabasePage(pBt, (Pgno)iTable, 0, 0);
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Erase all information in a table and add the root of the table to
** the freelist. Except, the root of the principle table (the one on
** page 1) is never added to the freelist.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** cursors on the table.
**
** If AUTOVACUUM is enabled and the page at iTable is not the last
** root page in the database file, then the last root page
** in the database file is moved into the slot formerly occupied by
** iTable and that last slot formerly occupied by the last root page
** is added to the freelist instead of iTable. In this say, all
** root pages are kept at the beginning of the database file, which
** is necessary for AUTOVACUUM to work right. *piMoved is set to the
** page number that used to be the last root page in the file before
** the move. If no page gets moved, *piMoved is set to 0.
** The last root page is recorded in meta[3] and the value of
** meta[3] is updated by this procedure.
*/
static int btreeDropTable(Btree *p, int iTable, int *piMoved){
int rc;
MemPage *pPage = 0;
BtShared *pBt = p->pBt;
assert( sqlite3BtreeHoldsMutex(p) );
if( p->inTrans!=TRANS_WRITE ){
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
/* It is illegal to drop a table if any cursors are open on the
** database. This is because in auto-vacuum mode the backend may
** need to move another root-page to fill a gap left by the deleted
** root page. If an open cursor was using this page a problem would
** occur.
*/
if( pBt->pCursor ){
return SQLITE_LOCKED;
}
rc = sqlite3BtreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
if( rc ) return rc;
rc = sqlite3BtreeClearTable(p, iTable);
if( rc ){
releasePage(pPage);
return rc;
}
*piMoved = 0;
if( iTable>1 ){
#ifdef SQLITE_OMIT_AUTOVACUUM
rc = freePage(pPage);
releasePage(pPage);
#else
if( pBt->autoVacuum ){
Pgno maxRootPgno;
rc = sqlite3BtreeGetMeta(p, 4, &maxRootPgno);
if( rc!=SQLITE_OK ){
releasePage(pPage);
return rc;
}
if( iTable==maxRootPgno ){
/* If the table being dropped is the table with the largest root-page
** number in the database, put the root page on the free list.
*/
rc = freePage(pPage);
releasePage(pPage);
if( rc!=SQLITE_OK ){
return rc;
}
}else{
/* The table being dropped does not have the largest root-page
** number in the database. So move the page that does into the
** gap left by the deleted root-page.
*/
MemPage *pMove;
releasePage(pPage);
rc = sqlite3BtreeGetPage(pBt, maxRootPgno, &pMove, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = relocatePage(pBt, pMove, PTRMAP_ROOTPAGE, 0, iTable);
releasePage(pMove);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3BtreeGetPage(pBt, maxRootPgno, &pMove, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = freePage(pMove);
releasePage(pMove);
if( rc!=SQLITE_OK ){
return rc;
}
*piMoved = maxRootPgno;
}
/* Set the new 'max-root-page' value in the database header. This
** is the old value less one, less one more if that happens to
** be a root-page number, less one again if that is the
** PENDING_BYTE_PAGE.
*/
maxRootPgno--;
if( maxRootPgno==PENDING_BYTE_PAGE(pBt) ){
maxRootPgno--;
}
if( maxRootPgno==PTRMAP_PAGENO(pBt, maxRootPgno) ){
maxRootPgno--;
}
assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );
rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
}else{
rc = freePage(pPage);
releasePage(pPage);
}
#endif
}else{
/* If sqlite3BtreeDropTable was called on page 1. */
zeroPage(pPage, PTF_INTKEY|PTF_LEAF );
releasePage(pPage);
}
return rc;
}
int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
int rc;
sqlite3BtreeEnter(p);
rc = btreeDropTable(p, iTable, piMoved);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Read the meta-information out of a database file. Meta[0]
** is the number of free pages currently in the database. Meta[1]
** through meta[15] are available for use by higher layers. Meta[0]
** is read-only, the others are read/write.
**
** The schema layer numbers meta values differently. At the schema
** layer (and the SetCookie and ReadCookie opcodes) the number of
** free pages is not visible. So Cookie[0] is the same as Meta[1].
*/
int sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
DbPage *pDbPage;
int rc;
unsigned char *pP1;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
/* Reading a meta-data value requires a read-lock on page 1 (and hence
** the sqlite_master table. We grab this lock regardless of whether or
** not the SQLITE_ReadUncommitted flag is set (the table rooted at page
** 1 is treated as a special case by queryTableLock() and lockTable()).
*/
rc = queryTableLock(p, 1, READ_LOCK);
if( rc!=SQLITE_OK ){
sqlite3BtreeLeave(p);
return rc;
}
assert( idx>=0 && idx<=15 );
rc = sqlite3PagerGet(pBt->pPager, 1, &pDbPage);
if( rc ){
sqlite3BtreeLeave(p);
return rc;
}
pP1 = (unsigned char *)sqlite3PagerGetData(pDbPage);
*pMeta = get4byte(&pP1[36 + idx*4]);
sqlite3PagerUnref(pDbPage);
/* If autovacuumed is disabled in this build but we are trying to
** access an autovacuumed database, then make the database readonly.
*/
#ifdef SQLITE_OMIT_AUTOVACUUM
if( idx==4 && *pMeta>0 ) pBt->readOnly = 1;
#endif
/* Grab the read-lock on page 1. */
rc = lockTable(p, 1, READ_LOCK);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Write meta-information back into the database. Meta[0] is
** read-only and may not be written.
*/
int sqlite3BtreeUpdateMeta(Btree *p, int idx, u32 iMeta){
BtShared *pBt = p->pBt;
unsigned char *pP1;
int rc;
assert( idx>=1 && idx<=15 );
sqlite3BtreeEnter(p);
if( p->inTrans!=TRANS_WRITE ){
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}else{
assert( pBt->pPage1!=0 );
pP1 = pBt->pPage1->aData;
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pP1[36 + idx*4], iMeta);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( idx==7 ){
assert( pBt->autoVacuum || iMeta==0 );
assert( iMeta==0 || iMeta==1 );
pBt->incrVacuum = iMeta;
}
#endif
}
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Return the flag byte at the beginning of the page that the cursor
** is currently pointing to.
*/
int sqlite3BtreeFlags(BtCursor *pCur){
/* TODO: What about CURSOR_REQUIRESEEK state? Probably need to call
** restoreOrClearCursorPosition() here.
*/
MemPage *pPage = pCur->pPage;
assert( cursorHoldsMutex(pCur) );
assert( pPage->pBt==pCur->pBt );
return pPage ? pPage->aData[pPage->hdrOffset] : 0;
}
/*
** Return the pager associated with a BTree. This routine is used for
** testing and debugging only.
*/
Pager *sqlite3BtreePager(Btree *p){
return p->pBt->pPager;
}
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Append a message to the error message string.
*/
static void checkAppendMsg(
IntegrityCk *pCheck,
char *zMsg1,
const char *zFormat,
...
){
va_list ap;
char *zMsg2;
if( !pCheck->mxErr ) return;
pCheck->mxErr--;
pCheck->nErr++;
va_start(ap, zFormat);
zMsg2 = sqlite3VMPrintf(0, zFormat, ap);
va_end(ap);
if( zMsg1==0 ) zMsg1 = "";
if( pCheck->zErrMsg ){
char *zOld = pCheck->zErrMsg;
pCheck->zErrMsg = 0;
sqlite3SetString(&pCheck->zErrMsg, zOld, "\n", zMsg1, zMsg2, (char*)0);
sqlite3_free(zOld);
}else{
sqlite3SetString(&pCheck->zErrMsg, zMsg1, zMsg2, (char*)0);
}
sqlite3_free(zMsg2);
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Add 1 to the reference count for page iPage. If this is the second
** reference to the page, add an error message to pCheck->zErrMsg.
** Return 1 if there are 2 ore more references to the page and 0 if
** if this is the first reference to the page.
**
** Also check that the page number is in bounds.
*/
static int checkRef(IntegrityCk *pCheck, int iPage, char *zContext){
if( iPage==0 ) return 1;
if( iPage>pCheck->nPage || iPage<0 ){
checkAppendMsg(pCheck, zContext, "invalid page number %d", iPage);
return 1;
}
if( pCheck->anRef[iPage]==1 ){
checkAppendMsg(pCheck, zContext, "2nd reference to page %d", iPage);
return 1;
}
return (pCheck->anRef[iPage]++)>1;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Check that the entry in the pointer-map for page iChild maps to
** page iParent, pointer type ptrType. If not, append an error message
** to pCheck.
*/
static void checkPtrmap(
IntegrityCk *pCheck, /* Integrity check context */
Pgno iChild, /* Child page number */
u8 eType, /* Expected pointer map type */
Pgno iParent, /* Expected pointer map parent page number */
char *zContext /* Context description (used for error msg) */
){
int rc;
u8 ePtrmapType;
Pgno iPtrmapParent;
rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
if( rc!=SQLITE_OK ){
checkAppendMsg(pCheck, zContext, "Failed to read ptrmap key=%d", iChild);
return;
}
if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
checkAppendMsg(pCheck, zContext,
"Bad ptr map entry key=%d expected=(%d,%d) got=(%d,%d)",
iChild, eType, iParent, ePtrmapType, iPtrmapParent);
}
}
#endif
/*
** Check the integrity of the freelist or of an overflow page list.
** Verify that the number of pages on the list is N.
*/
static void checkList(
IntegrityCk *pCheck, /* Integrity checking context */
int isFreeList, /* True for a freelist. False for overflow page list */
int iPage, /* Page number for first page in the list */
int N, /* Expected number of pages in the list */
char *zContext /* Context for error messages */
){
int i;
int expected = N;
int iFirst = iPage;
while( N-- > 0 && pCheck->mxErr ){
DbPage *pOvflPage;
unsigned char *pOvflData;
if( iPage<1 ){
checkAppendMsg(pCheck, zContext,
"%d of %d pages missing from overflow list starting at %d",
N+1, expected, iFirst);
break;
}
if( checkRef(pCheck, iPage, zContext) ) break;
if( sqlite3PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage) ){
checkAppendMsg(pCheck, zContext, "failed to get page %d", iPage);
break;
}
pOvflData = (unsigned char *)sqlite3PagerGetData(pOvflPage);
if( isFreeList ){
int n = get4byte(&pOvflData[4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pCheck->pBt->autoVacuum ){
checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0, zContext);
}
#endif
if( n>pCheck->pBt->usableSize/4-8 ){
checkAppendMsg(pCheck, zContext,
"freelist leaf count too big on page %d", iPage);
N--;
}else{
for(i=0; i<n; i++){
Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pCheck->pBt->autoVacuum ){
checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0, zContext);
}
#endif
checkRef(pCheck, iFreePage, zContext);
}
N -= n;
}
}
#ifndef SQLITE_OMIT_AUTOVACUUM
else{
/* If this database supports auto-vacuum and iPage is not the last
** page in this overflow list, check that the pointer-map entry for
** the following page matches iPage.
*/
if( pCheck->pBt->autoVacuum && N>0 ){
i = get4byte(pOvflData);
checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage, zContext);
}
}
#endif
iPage = get4byte(pOvflData);
sqlite3PagerUnref(pOvflPage);
}
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Do various sanity checks on a single page of a tree. Return
** the tree depth. Root pages return 0. Parents of root pages
** return 1, and so forth.
**
** These checks are done:
**
** 1. Make sure that cells and freeblocks do not overlap
** but combine to completely cover the page.
** NO 2. Make sure cell keys are in order.
** NO 3. Make sure no key is less than or equal to zLowerBound.
** NO 4. Make sure no key is greater than or equal to zUpperBound.
** 5. Check the integrity of overflow pages.
** 6. Recursively call checkTreePage on all children.
** 7. Verify that the depth of all children is the same.
** 8. Make sure this page is at least 33% full or else it is
** the root of the tree.
*/
static int checkTreePage(
IntegrityCk *pCheck, /* Context for the sanity check */
int iPage, /* Page number of the page to check */
MemPage *pParent, /* Parent page */
char *zParentContext /* Parent context */
){
MemPage *pPage;
int i, rc, depth, d2, pgno, cnt;
int hdr, cellStart;
int nCell;
u8 *data;
BtShared *pBt;
int usableSize;
char zContext[100];
char *hit;
sqlite3_snprintf(sizeof(zContext), zContext, "Page %d: ", iPage);
/* Check that the page exists
*/
pBt = pCheck->pBt;
usableSize = pBt->usableSize;
if( iPage==0 ) return 0;
if( checkRef(pCheck, iPage, zParentContext) ) return 0;
if( (rc = sqlite3BtreeGetPage(pBt, (Pgno)iPage, &pPage, 0))!=0 ){
checkAppendMsg(pCheck, zContext,
"unable to get the page. error code=%d", rc);
return 0;
}
if( (rc = sqlite3BtreeInitPage(pPage, pParent))!=0 ){
checkAppendMsg(pCheck, zContext,
"sqlite3BtreeInitPage() returns error code %d", rc);
releasePage(pPage);
return 0;
}
/* Check out all the cells.
*/
depth = 0;
for(i=0; i<pPage->nCell && pCheck->mxErr; i++){
u8 *pCell;
int sz;
CellInfo info;
/* Check payload overflow pages
*/
sqlite3_snprintf(sizeof(zContext), zContext,
"On tree page %d cell %d: ", iPage, i);
pCell = findCell(pPage,i);
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
sz = info.nData;
if( !pPage->intKey ) sz += info.nKey;
assert( sz==info.nPayload );
if( sz>info.nLocal ){
int nPage = (sz - info.nLocal + usableSize - 5)/(usableSize - 4);
Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage, zContext);
}
#endif
checkList(pCheck, 0, pgnoOvfl, nPage, zContext);
}
/* Check sanity of left child page.
*/
if( !pPage->leaf ){
pgno = get4byte(pCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, zContext);
}
#endif
d2 = checkTreePage(pCheck,pgno,pPage,zContext);
if( i>0 && d2!=depth ){
checkAppendMsg(pCheck, zContext, "Child page depth differs");
}
depth = d2;
}
}
if( !pPage->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
sqlite3_snprintf(sizeof(zContext), zContext,
"On page %d at right child: ", iPage);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, 0);
}
#endif
checkTreePage(pCheck, pgno, pPage, zContext);
}
/* Check for complete coverage of the page
*/
data = pPage->aData;
hdr = pPage->hdrOffset;
hit = sqlite3MallocZero( usableSize );
if( hit ){
memset(hit, 1, get2byte(&data[hdr+5]));
nCell = get2byte(&data[hdr+3]);
cellStart = hdr + 12 - 4*pPage->leaf;
for(i=0; i<nCell; i++){
int pc = get2byte(&data[cellStart+i*2]);
int size = cellSizePtr(pPage, &data[pc]);
int j;
if( (pc+size-1)>=usableSize || pc<0 ){
checkAppendMsg(pCheck, 0,
"Corruption detected in cell %d on page %d",i,iPage,0);
}else{
for(j=pc+size-1; j>=pc; j--) hit[j]++;
}
}
for(cnt=0, i=get2byte(&data[hdr+1]); i>0 && i<usableSize && cnt<10000;
cnt++){
int size = get2byte(&data[i+2]);
int j;
if( (i+size-1)>=usableSize || i<0 ){
checkAppendMsg(pCheck, 0,
"Corruption detected in cell %d on page %d",i,iPage,0);
}else{
for(j=i+size-1; j>=i; j--) hit[j]++;
}
i = get2byte(&data[i]);
}
for(i=cnt=0; i<usableSize; i++){
if( hit[i]==0 ){
cnt++;
}else if( hit[i]>1 ){
checkAppendMsg(pCheck, 0,
"Multiple uses for byte %d of page %d", i, iPage);
break;
}
}
if( cnt!=data[hdr+7] ){
checkAppendMsg(pCheck, 0,
"Fragmented space is %d byte reported as %d on page %d",
cnt, data[hdr+7], iPage);
}
}
sqlite3_free(hit);
releasePage(pPage);
return depth+1;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** This routine does a complete check of the given BTree file. aRoot[] is
** an array of pages numbers were each page number is the root page of
** a table. nRoot is the number of entries in aRoot.
**
** If everything checks out, this routine returns NULL. If something is
** amiss, an error message is written into memory obtained from malloc()
** and a pointer to that error message is returned. The calling function
** is responsible for freeing the error message when it is done.
*/
char *sqlite3BtreeIntegrityCheck(
Btree *p, /* The btree to be checked */
int *aRoot, /* An array of root pages numbers for individual trees */
int nRoot, /* Number of entries in aRoot[] */
int mxErr, /* Stop reporting errors after this many */
int *pnErr /* Write number of errors seen to this variable */
){
int i;
int nRef;
IntegrityCk sCheck;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
nRef = sqlite3PagerRefcount(pBt->pPager);
if( lockBtreeWithRetry(p)!=SQLITE_OK ){
sqlite3BtreeLeave(p);
return sqlite3StrDup("Unable to acquire a read lock on the database");
}
sCheck.pBt = pBt;
sCheck.pPager = pBt->pPager;
sCheck.nPage = sqlite3PagerPagecount(sCheck.pPager);
sCheck.mxErr = mxErr;
sCheck.nErr = 0;
*pnErr = 0;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->nTrunc!=0 ){
sCheck.nPage = pBt->nTrunc;
}
#endif
if( sCheck.nPage==0 ){
unlockBtreeIfUnused(pBt);
sqlite3BtreeLeave(p);
return 0;
}
sCheck.anRef = sqlite3_malloc( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
if( !sCheck.anRef ){
unlockBtreeIfUnused(pBt);
*pnErr = 1;
sqlite3BtreeLeave(p);
return sqlite3MPrintf(p->pSqlite, "Unable to malloc %d bytes",
(sCheck.nPage+1)*sizeof(sCheck.anRef[0]));
}
for(i=0; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }
i = PENDING_BYTE_PAGE(pBt);
if( i<=sCheck.nPage ){
sCheck.anRef[i] = 1;
}
sCheck.zErrMsg = 0;
/* Check the integrity of the freelist
*/
checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
get4byte(&pBt->pPage1->aData[36]), "Main freelist: ");
/* Check all the tables.
*/
for(i=0; i<nRoot && sCheck.mxErr; i++){
if( aRoot[i]==0 ) continue;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum && aRoot[i]>1 ){
checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0, 0);
}
#endif
checkTreePage(&sCheck, aRoot[i], 0, "List of tree roots: ");
}
/* Make sure every page in the file is referenced
*/
for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
#ifdef SQLITE_OMIT_AUTOVACUUM
if( sCheck.anRef[i]==0 ){
checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
}
#else
/* If the database supports auto-vacuum, make sure no tables contain
** references to pointer-map pages.
*/
if( sCheck.anRef[i]==0 &&
(PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
}
if( sCheck.anRef[i]!=0 &&
(PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
checkAppendMsg(&sCheck, 0, "Pointer map page %d is referenced", i);
}
#endif
}
/* Make sure this analysis did not leave any unref() pages
*/
unlockBtreeIfUnused(pBt);
if( nRef != sqlite3PagerRefcount(pBt->pPager) ){
checkAppendMsg(&sCheck, 0,
"Outstanding page count goes from %d to %d during this analysis",
nRef, sqlite3PagerRefcount(pBt->pPager)
);
}
/* Clean up and report errors.
*/
sqlite3BtreeLeave(p);
sqlite3_free(sCheck.anRef);
*pnErr = sCheck.nErr;
return sCheck.zErrMsg;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
/*
** Return the full pathname of the underlying database file.
**
** The pager filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetFilename(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerFilename(p->pBt->pPager);
}
/*
** Return the pathname of the directory that contains the database file.
**
** The pager directory name is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetDirname(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerDirname(p->pBt->pPager);
}
/*
** Return the pathname of the journal file for this database. The return
** value of this routine is the same regardless of whether the journal file
** has been created or not.
**
** The pager journal filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetJournalname(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerJournalname(p->pBt->pPager);
}
#ifndef SQLITE_OMIT_VACUUM
/*
** Copy the complete content of pBtFrom into pBtTo. A transaction
** must be active for both files.
**
** The size of file pBtFrom may be reduced by this operation.
** If anything goes wrong, the transaction on pBtFrom is rolled back.
*/
static int btreeCopyFile(Btree *pTo, Btree *pFrom){
int rc = SQLITE_OK;
Pgno i, nPage, nToPage, iSkip;
BtShared *pBtTo = pTo->pBt;
BtShared *pBtFrom = pFrom->pBt;
if( pTo->inTrans!=TRANS_WRITE || pFrom->inTrans!=TRANS_WRITE ){
return SQLITE_ERROR;
}
if( pBtTo->pCursor ) return SQLITE_BUSY;
nToPage = sqlite3PagerPagecount(pBtTo->pPager);
nPage = sqlite3PagerPagecount(pBtFrom->pPager);
iSkip = PENDING_BYTE_PAGE(pBtTo);
for(i=1; rc==SQLITE_OK && i<=nPage; i++){
DbPage *pDbPage;
if( i==iSkip ) continue;
rc = sqlite3PagerGet(pBtFrom->pPager, i, &pDbPage);
if( rc ) break;
rc = sqlite3PagerOverwrite(pBtTo->pPager, i, sqlite3PagerGetData(pDbPage));
sqlite3PagerUnref(pDbPage);
}
/* If the file is shrinking, journal the pages that are being truncated
** so that they can be rolled back if the commit fails.
*/
for(i=nPage+1; rc==SQLITE_OK && i<=nToPage; i++){
DbPage *pDbPage;
if( i==iSkip ) continue;
rc = sqlite3PagerGet(pBtTo->pPager, i, &pDbPage);
if( rc ) break;
rc = sqlite3PagerWrite(pDbPage);
sqlite3PagerDontWrite(pDbPage);
/* Yeah. It seems wierd to call DontWrite() right after Write(). But
** that is because the names of those procedures do not exactly
** represent what they do. Write() really means "put this page in the
** rollback journal and mark it as dirty so that it will be written
** to the database file later." DontWrite() undoes the second part of
** that and prevents the page from being written to the database. The
** page is still on the rollback journal, though. And that is the whole
** point of this loop: to put pages on the rollback journal. */
sqlite3PagerUnref(pDbPage);
}
if( !rc && nPage<nToPage ){
rc = sqlite3PagerTruncate(pBtTo->pPager, nPage);
}
if( rc ){
sqlite3BtreeRollback(pTo);
}
return rc;
}
int sqlite3BtreeCopyFile(Btree *pTo, Btree *pFrom){
int rc;
sqlite3BtreeEnter(pTo);
sqlite3BtreeEnter(pFrom);
rc = btreeCopyFile(pTo, pFrom);
sqlite3BtreeLeave(pFrom);
sqlite3BtreeLeave(pTo);
return rc;
}
#endif /* SQLITE_OMIT_VACUUM */
/*
** Return non-zero if a transaction is active.
*/
int sqlite3BtreeIsInTrans(Btree *p){
assert( p==0 || sqlite3_mutex_held(p->pSqlite->mutex) );
return (p && (p->inTrans==TRANS_WRITE));
}
/*
** Return non-zero if a statement transaction is active.
*/
int sqlite3BtreeIsInStmt(Btree *p){
assert( sqlite3BtreeHoldsMutex(p) );
return (p->pBt && p->pBt->inStmt);
}
/*
** Return non-zero if a read (or write) transaction is active.
*/
int sqlite3BtreeIsInReadTrans(Btree *p){
assert( sqlite3_mutex_held(p->pSqlite->mutex) );
return (p && (p->inTrans!=TRANS_NONE));
}
/*
** This function returns a pointer to a blob of memory associated with
** a single shared-btree. The memory is used by client code for it's own
** purposes (for example, to store a high-level schema associated with
** the shared-btree). The btree layer manages reference counting issues.
**
** The first time this is called on a shared-btree, nBytes bytes of memory
** are allocated, zeroed, and returned to the caller. For each subsequent
** call the nBytes parameter is ignored and a pointer to the same blob
** of memory returned.
**
** Just before the shared-btree is closed, the function passed as the
** xFree argument when the memory allocation was made is invoked on the
** blob of allocated memory. This function should not call sqlite3_free()
** on the memory, the btree layer does that.
*/
void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( !pBt->pSchema ){
pBt->pSchema = sqlite3MallocZero(nBytes);
pBt->xFreeSchema = xFree;
}
sqlite3BtreeLeave(p);
return pBt->pSchema;
}
/*
** Return true if another user of the same shared btree as the argument
** handle holds an exclusive lock on the sqlite_master table.
*/
int sqlite3BtreeSchemaLocked(Btree *p){
int rc;
assert( sqlite3_mutex_held(p->pSqlite->mutex) );
sqlite3BtreeEnter(p);
rc = (queryTableLock(p, MASTER_ROOT, READ_LOCK)!=SQLITE_OK);
sqlite3BtreeLeave(p);
return rc;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Obtain a lock on the table whose root page is iTab. The
** lock is a write lock if isWritelock is true or a read lock
** if it is false.
*/
int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
int rc = SQLITE_OK;
u8 lockType = (isWriteLock?WRITE_LOCK:READ_LOCK);
sqlite3BtreeEnter(p);
rc = queryTableLock(p, iTab, lockType);
if( rc==SQLITE_OK ){
rc = lockTable(p, iTab, lockType);
}
sqlite3BtreeLeave(p);
return rc;
}
#endif
#ifndef SQLITE_OMIT_INCRBLOB
/*
** Argument pCsr must be a cursor opened for writing on an
** INTKEY table currently pointing at a valid table entry.
** This function modifies the data stored as part of that entry.
** Only the data content may only be modified, it is not possible
** to change the length of the data stored.
*/
int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
assert( cursorHoldsMutex(pCsr) );
assert( sqlite3_mutex_held(pCsr->pBtree->pSqlite->mutex) );
assert(pCsr->isIncrblobHandle);
if( pCsr->eState>=CURSOR_REQUIRESEEK ){
if( pCsr->eState==CURSOR_FAULT ){
return pCsr->skip;
}else{
return SQLITE_ABORT;
}
}
/* Check some preconditions:
** (a) the cursor is open for writing,
** (b) there is no read-lock on the table being modified and
** (c) the cursor points at a valid row of an intKey table.
*/
if( !pCsr->wrFlag ){
return SQLITE_READONLY;
}
assert( !pCsr->pBt->readOnly
&& pCsr->pBt->inTransaction==TRANS_WRITE );
if( checkReadLocks(pCsr->pBtree, pCsr->pgnoRoot, pCsr) ){
return SQLITE_LOCKED; /* The table pCur points to has a read lock */
}
if( pCsr->eState==CURSOR_INVALID || !pCsr->pPage->intKey ){
return SQLITE_ERROR;
}
return accessPayload(pCsr, offset, amt, (unsigned char *)z, 0, 1);
}
/*
** Set a flag on this cursor to cache the locations of pages from the
** overflow list for the current row. This is used by cursors opened
** for incremental blob IO only.
**
** This function sets a flag only. The actual page location cache
** (stored in BtCursor.aOverflow[]) is allocated and used by function
** accessPayload() (the worker function for sqlite3BtreeData() and
** sqlite3BtreePutData()).
*/
void sqlite3BtreeCacheOverflow(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
assert(!pCur->isIncrblobHandle);
assert(!pCur->aOverflow);
pCur->isIncrblobHandle = 1;
}
#endif
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