数据库系统

开发平台：

C/C++

btree.c：源码内容

** 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 */
UnpackedRecord *pUnKey,/* Unpacked version of pKey */
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;
char aSpace[200];
assert( cursorHoldsMutex(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
/* If the cursor is already positioned at the point we are trying
** to move to, then just return without doing any work */
if( pCur->eState==CURSOR_VALID && pCur->validNKey && pCur->pPage->intKey ){
if( pCur->info.nKey==nKey ){
*pRes = 0;
return SQLITE_OK;
}
if( pCur->atLast && pCur->info.nKey<nKey ){
*pRes = -1;
return SQLITE_OK;
}
}
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;
}
if( pCur->pPage->intKey ){
/* We are given an SQL table to search. The key is the integer
** rowid contained in nKey. pKey and pUnKey should both be NULL */
assert( pUnKey==0 );
assert( pKey==0 );
}else if( pUnKey==0 ){
/* We are to search an SQL index using a key encoded as a blob.
** The blob is found at pKey and is nKey bytes in length. Unpack
** this key so that we can use it. */
assert( pKey!=0 );
pUnKey = sqlite3VdbeRecordUnpack(pCur->pKeyInfo, nKey, pKey,
aSpace, sizeof(aSpace));
if( pUnKey==0 ) return SQLITE_NOMEM;
}else{
/* We are to search an SQL index using a key that is already unpacked
** and handed to us in pUnKey. */
assert( pKey==0 );
}
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 && pUnKey==0 ){
rc = SQLITE_CORRUPT_BKPT;
goto moveto_finish;
}
if( biasRight ){
pCur->idx = upr;
}else{
pCur->idx = (upr+lwr)/2;
}
if( lwr<=upr ) for(;;){
void *pCellKey;
i64 nCellKey;
pCur->info.nSize = 0;
pCur->validNKey = 1;
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 = 0;
}else if( nCellKey<nKey ){
c = -1;
}else{
assert( nCellKey>nKey );
c = +1;
}
}else{
int available;
pCellKey = (void *)fetchPayload(pCur, &available, 0);
nCellKey = pCur->info.nKey;
if( available>=nCellKey ){
c = sqlite3VdbeRecordCompare(nCellKey, pCellKey, pUnKey);
}else{
pCellKey = sqlite3_malloc( nCellKey );
if( pCellKey==0 ){
rc = SQLITE_NOMEM;
goto moveto_finish;
}
rc = sqlite3BtreeKey(pCur, 0, nCellKey, (void *)pCellKey);
c = sqlite3VdbeRecordCompare(nCellKey, pCellKey, pUnKey);
sqlite3_free(pCellKey);
if( rc ) goto moveto_finish;
}
}
if( c==0 ){
pCur->info.nKey = nCellKey;
if( pPage->leafData && !pPage->leaf ){
lwr = pCur->idx;
upr = lwr - 1;
break;
}else{
if( pRes ) *pRes = 0;
rc = SQLITE_OK;
goto moveto_finish;
}
}
if( c<0 ){
lwr = pCur->idx+1;
}else{
upr = pCur->idx-1;
}
if( lwr>upr ){
pCur->info.nKey = nCellKey;
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;
rc = SQLITE_OK;
goto moveto_finish;
}
pCur->idx = lwr;
pCur->info.nSize = 0;
pCur->validNKey = 0;
rc = moveToChild(pCur, chldPg);
if( rc ) goto moveto_finish;
}
moveto_finish:
if( pKey ){
/* If we created our own unpacked key at the top of this
** procedure, then destroy that key before returning. */
sqlite3VdbeDeleteUnpackedRecord(pUnKey);
}
return rc;
}
/*
** 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->db->mutex) );
return pCur->pBtree->db;
}
/*
** 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.
*/
int sqlite3BtreeNext(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;
pCur->validNKey = 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;
}
/*
** 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.
*/
int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
int rc;
Pgno pgno;
MemPage *pPage;
assert( cursorHoldsMutex(pCur) );
rc = restoreOrClearCursorPosition(pCur);
if( rc!=SQLITE_OK ){
return rc;
}
pCur->atLast = 0;
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;
pCur->validNKey = 0;
if( pPage->leafData && !pPage->leaf ){
rc = sqlite3BtreePrevious(pCur, pRes);
}else{
rc = SQLITE_OK;
}
}
*pRes = 0;
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 leftn", *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 leftn", *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 pagesn",
*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( *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 filen", *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 firstn", 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 %dn",
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 %dn",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);
rc = reparentPage(pBt, get4byte(pCell), pPage, i);
if( rc!=SQLITE_OK ) return rc;
}
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 */
u16 *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;
u16 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 */
u16 *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 %dn", 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 4 in order to preserve 8-byte
** alignment */
nMaxCells = (nMaxCells + 3)&~3;
/*
** Allocate space for memory structures
*/
apCell = sqlite3_malloc(
nMaxCells*sizeof(u8*) /* apCell */
+ nMaxCells*sizeof(u16) /* szCell */
+ (ROUND8(sizeof(MemPage))+pBt->pageSize)*NB /* aCopy */
+ pBt->pageSize*5 /* aSpace */
+ (ISAUTOVACUUM ? nMaxCells : 0) /* aFrom */
);
if( apCell==0 ){
rc = SQLITE_NOMEM;
goto balance_cleanup;
}
szCell = (u16*)&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 ){
u16 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 its 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 is 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=%dn",
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 */
u16 *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(u16)) );
if( apCell==0 ) return SQLITE_NOMEM;
szCell = (u16*)&apCell[mxCellPerPage];
if( pPage->leaf ){
/* The table is completely empty */
TRACE(("BALANCE: empty table %dn", 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 1n", 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 1n", 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 %dn",
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 %dn", 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->db;
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->db;
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;
}
/*
** Make sure pBt->pTmpSpace points to an allocation of
** MX_CELL_SIZE(pBt) bytes.
*/
static void allocateTempSpace(BtShared *pBt){
if( !pBt->pTmpSpace ){
pBt->pTmpSpace = sqlite3_malloc(MX_CELL_SIZE(pBt));
}
}
/*
** 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, 0, 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 %sn",
pCur->pgnoRoot, nKey, nData, pPage->pgno,
loc==0 ? "overwrite" : "new entry"));
assert( pPage->isInit );
allocateTempSpace(pBt);
newCell = pBt->pTmpSpace;
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 ){
u16 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;
pCur->validNKey = 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:
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 its 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 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 ){
u16 szNext;
TRACE(("DELETE: table=%d delete internal from %d replace from leaf %dn",
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 );
allocateTempSpace(pBt);
tempCell = pBt->pTmpSpace;
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);
}
}
sqlite3BtreeReleaseTempCursor(&leafCur);
}else{
TRACE(("DELETE: table=%d delete from leaf %dn",
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.
*/
while( 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);
p->pBt->db = p->db;
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);
pBt->db = p->db;
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);
p->pBt->db = p->db;
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);
pBt->db = p->db;
/* 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);
pBt->db = p->db;
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;
restoreOrClearCursorPosition(pCur);
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]);
u16 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);
pBt->db = p->db;
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->db, "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 pTo may be reduced by this operation.
** If anything goes wrong, the transaction on pTo is rolled back.
**
** If successful, CommitPhaseOne() may be called on pTo before returning.
** The caller should finish committing the transaction on pTo by calling
** sqlite3BtreeCommit().
*/
static int btreeCopyFile(Btree *pTo, Btree *pFrom){
int rc = SQLITE_OK;
Pgno i;
Pgno nFromPage; /* Number of pages in pFrom */
Pgno nToPage; /* Number of pages in pTo */
Pgno nNewPage; /* Number of pages in pTo after the copy */
Pgno iSkip; /* Pending byte page in pTo */
int nToPageSize; /* Page size of pTo in bytes */
int nFromPageSize; /* Page size of pFrom in bytes */
BtShared *pBtTo = pTo->pBt;
BtShared *pBtFrom = pFrom->pBt;
pBtTo->db = pTo->db;
pBtFrom->db = pFrom->db;
nToPageSize = pBtTo->pageSize;
nFromPageSize = pBtFrom->pageSize;
if( pTo->inTrans!=TRANS_WRITE || pFrom->inTrans!=TRANS_WRITE ){
return SQLITE_ERROR;
}
if( pBtTo->pCursor ){
return SQLITE_BUSY;
}
nToPage = sqlite3PagerPagecount(pBtTo->pPager);
nFromPage = sqlite3PagerPagecount(pBtFrom->pPager);
iSkip = PENDING_BYTE_PAGE(pBtTo);
/* Variable nNewPage is the number of pages required to store the
** contents of pFrom using the current page-size of pTo.
*/
nNewPage = ((i64)nFromPage * (i64)nFromPageSize + (i64)nToPageSize - 1) /
(i64)nToPageSize;
for(i=1; rc==SQLITE_OK && (i<=nToPage || i<=nNewPage); i++){
/* Journal the original page.
**
** iSkip is the page number of the locking page (PENDING_BYTE_PAGE)
** in database *pTo (before the copy). This page is never written
** into the journal file. Unless i==iSkip or the page was not
** present in pTo before the copy operation, journal page i from pTo.
*/
if( i!=iSkip && i<=nToPage ){
DbPage *pDbPage;
rc = sqlite3PagerGet(pBtTo->pPager, i, &pDbPage);
if( rc ){
break;
}
rc = sqlite3PagerWrite(pDbPage);
if( rc ){
break;
}
if( i>nFromPage ){
/* 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 block: to put pages on the rollback journal.
*/
sqlite3PagerDontWrite(pDbPage);
}
sqlite3PagerUnref(pDbPage);
}
/* Overwrite the data in page i of the target database */
if( rc==SQLITE_OK && i!=iSkip && i<=nNewPage ){
DbPage *pToPage = 0;
sqlite3_int64 iOff;
rc = sqlite3PagerGet(pBtTo->pPager, i, &pToPage);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pToPage);
}
for(
iOff=(i-1)*nToPageSize;
rc==SQLITE_OK && iOff<i*nToPageSize;
iOff += nFromPageSize
){
DbPage *pFromPage = 0;
Pgno iFrom = (iOff/nFromPageSize)+1;
if( iFrom==PENDING_BYTE_PAGE(pBtFrom) ){
continue;
}
rc = sqlite3PagerGet(pBtFrom->pPager, iFrom, &pFromPage);
if( rc==SQLITE_OK ){
char *zTo = sqlite3PagerGetData(pToPage);
char *zFrom = sqlite3PagerGetData(pFromPage);
int nCopy;
if( nFromPageSize>=nToPageSize ){
zFrom += ((i-1)*nToPageSize - ((iFrom-1)*nFromPageSize));
nCopy = nToPageSize;
}else{
zTo += (((iFrom-1)*nFromPageSize) - (i-1)*nToPageSize);
nCopy = nFromPageSize;
}
memcpy(zTo, zFrom, nCopy);
sqlite3PagerUnref(pFromPage);
}
}
if( pToPage ) sqlite3PagerUnref(pToPage);
}
}
/* If things have worked so far, the database file may need to be
** truncated. The complex part is that it may need to be truncated to
** a size that is not an integer multiple of nToPageSize - the current
** page size used by the pager associated with B-Tree pTo.
**
** For example, say the page-size of pTo is 2048 bytes and the original
** number of pages is 5 (10 KB file). If pFrom has a page size of 1024
** bytes and 9 pages, then the file needs to be truncated to 9KB.
*/
if( rc==SQLITE_OK ){
if( nFromPageSize!=nToPageSize ){
sqlite3_file *pFile = sqlite3PagerFile(pBtTo->pPager);
i64 iSize = (i64)nFromPageSize * (i64)nFromPage;
i64 iNow = (i64)((nToPage>nNewPage)?nToPage:nNewPage) * (i64)nToPageSize;
i64 iPending = ((i64)PENDING_BYTE_PAGE(pBtTo)-1) *(i64)nToPageSize;
assert( iSize<=iNow );
/* Commit phase one syncs the journal file associated with pTo
** containing the original data. It does not sync the database file
** itself. After doing this it is safe to use OsTruncate() and other
** file APIs on the database file directly.
*/
pBtTo->db = pTo->db;
rc = sqlite3PagerCommitPhaseOne(pBtTo->pPager, 0, 0, 1);
if( iSize<iNow && rc==SQLITE_OK ){
rc = sqlite3OsTruncate(pFile, iSize);
}
/* The loop that copied data from database pFrom to pTo did not
** populate the locking page of database pTo. If the page-size of
** pFrom is smaller than that of pTo, this means some data will
** not have been copied.
**
** This block copies the missing data from database pFrom to pTo
** using file APIs. This is safe because at this point we know that
** all of the original data from pTo has been synced into the
** journal file. At this point it would be safe to do anything at
** all to the database file except truncate it to zero bytes.
*/
if( rc==SQLITE_OK && nFromPageSize<nToPageSize && iSize>iPending){
i64 iOff;
for(
iOff=iPending;
rc==SQLITE_OK && iOff<(iPending+nToPageSize);
iOff += nFromPageSize
){
DbPage *pFromPage = 0;
Pgno iFrom = (iOff/nFromPageSize)+1;
if( iFrom==PENDING_BYTE_PAGE(pBtFrom) || iFrom>nFromPage ){
continue;
}
rc = sqlite3PagerGet(pBtFrom->pPager, iFrom, &pFromPage);
if( rc==SQLITE_OK ){
char *zFrom = sqlite3PagerGetData(pFromPage);
rc = sqlite3OsWrite(pFile, zFrom, nFromPageSize, iOff);
sqlite3PagerUnref(pFromPage);
}
}
}
/* Sync the database file */
if( rc==SQLITE_OK ){
rc = sqlite3PagerSync(pBtTo->pPager);
}
}else{
rc = sqlite3PagerTruncate(pBtTo->pPager, nNewPage);
}
if( rc==SQLITE_OK ){
pBtTo->pageSizeFixed = 0;
}
}
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->db->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->db->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 its 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->db->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;
if( p->sharable ){
u8 lockType = READ_LOCK + isWriteLock;
assert( READ_LOCK+1==WRITE_LOCK );
assert( isWriteLock==0 || isWriteLock==1 );
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->db->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->db->mutex) );
assert(!pCur->isIncrblobHandle);
assert(!pCur->aOverflow);
pCur->isIncrblobHandle = 1;
}
#endif