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Cache the location of overflow pages in cursors used for incremental blob IO. (CVS 3899)

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FossilOrigin-Name: 349f1ea7895f06c40affc985a13aa6686dfdea07
This commit is contained in:
danielk1977
2007-05-02 16:48:37 +00:00
parent 7a928d75f4
commit 2dec97077b
5 changed files with 138 additions and 51 deletions
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163
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.365 2007/05/02 13:16:30 danielk1977 Exp $
** $Id: btree.c,v 1.366 2007/05/02 16:48:37 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
@@ -394,6 +394,10 @@ struct BtCursor {
void *pKey; /* Saved key that was cursor's last known position */
i64 nKey; /* Size of pKey, or last integer key */
int skip; /* (skip<0) -> Prev() is a no-op. (skip>0) -> Next() is */
#ifndef SQLITE_OMIT_INCRBLOB
u8 cacheOverflow; /* True to use aOverflow */
Pgno *aOverflow; /* Cache of overflow page locations */
#endif
};
/*
@@ -691,6 +695,12 @@ static int saveCursorPosition(BtCursor *pCur){
pCur->eState = CURSOR_REQUIRESEEK;
}
#ifndef SQLITE_OMIT_INCRBLOB
/* Delete the cache of overflow page numbers. */
sqliteFree(pCur->aOverflow);
pCur->aOverflow = 0;
#endif
return rc;
}
@@ -2413,13 +2423,20 @@ static int incrVacuumStep(BtShared *pBt, Pgno nFin){
*/
int sqlite3BtreeIncrVacuum(Btree *p){
BtShared *pBt = p->pBt;
BtCursor *pCur;
assert( pBt->inTransaction==TRANS_WRITE && p->inTrans==TRANS_WRITE );
if( !pBt->autoVacuum ){
return SQLITE_DONE;
}
return incrVacuumStep(p->pBt, 0);
#ifndef SQLITE_OMIT_INCRBLOB
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
/* Delete the cache of overflow page numbers. */
sqliteFree(pCur->aOverflow);
pCur->aOverflow = 0;
}
#endif
return incrVacuumStep(pBt, 0);
}
/*
@@ -2438,6 +2455,15 @@ static int autoVacuumCommit(BtShared *pBt, Pgno *pnTrunc){
int nRef = sqlite3PagerRefcount(pPager);
#endif
#ifndef SQLITE_OMIT_INCRBLOB
BtCursor *pCur;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
/* Delete the cache of overflow page numbers. */
sqliteFree(pCur->aOverflow);
pCur->aOverflow = 0;
}
#endif
assert(pBt->autoVacuum);
if( !pBt->incrVacuum ){
Pgno nFin = 0;
@@ -2933,6 +2959,9 @@ int sqlite3BtreeCloseCursor(BtCursor *pCur){
}
releasePage(pCur->pPage);
unlockBtreeIfUnused(pBt);
#ifndef SQLITE_OMIT_INCRBLOB
sqliteFree(pCur->aOverflow);
#endif
sqliteFree(pCur);
return SQLITE_OK;
}
@@ -3132,6 +3161,7 @@ static int getPayload(
BtShared *pBt;
int ovflSize;
u32 nKey;
int iIdx = 0;
assert( pCur!=0 && pCur->pPage!=0 );
assert( pCur->eState==CURSOR_VALID );
@@ -3170,7 +3200,21 @@ static int getPayload(
ovflSize = pBt->usableSize - 4;
if( amt>0 ){
nextPage = get4byte(&aPayload[pCur->info.nLocal]);
while( amt>0 && nextPage ){
#ifndef SQLITE_OMIT_INCRBLOB
if( pCur->cacheOverflow && !pCur->aOverflow ){
int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
pCur->aOverflow = (Pgno *)sqliteMalloc(sizeof(Pgno)*nOvfl);
if( nOvfl && !pCur->aOverflow ){
return SQLITE_NOMEM;
}
}
if( pCur->aOverflow && pCur->aOverflow[offset/ovflSize] ){
iIdx = (offset/ovflSize);
nextPage = pCur->aOverflow[iIdx];
offset = (offset%ovflSize);
}
#endif
for(iIdx++; amt>0 && nextPage; iIdx++){
if( offset>=ovflSize ){
/* The only reason to read this page is to obtain the page
** number for the next page in the overflow chain. So try
@@ -3181,6 +3225,12 @@ static int getPayload(
return rc;
}
offset -= ovflSize;
#ifndef SQLITE_OMIT_INCRBLOB
if( pCur->aOverflow ){
assert(nextPage);
pCur->aOverflow[iIdx] = nextPage;
}
#endif
}else{
/* Need to read this page properly, to obtain data to copy into
** the caller's buffer.
@@ -3201,6 +3251,11 @@ static int getPayload(
amt -= a;
pBuf += a;
sqlite3PagerUnref(pDbPage);
#ifndef SQLITE_OMIT_INCRBLOB
if( pCur->aOverflow && nextPage ){
pCur->aOverflow[iIdx] = nextPage;
}
#endif
}
}
}
@@ -6874,6 +6929,7 @@ int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, const void *z){
u8 *zRem = (u8 *)z; /* Pointer to data not yet written */
u32 iOffset = offset; /* Offset from traversal point to start of write */
Pgno iIdx = 0; /* Index of overflow page in pCsr->aOverflow */
Pgno iOvfl; /* Page number for next overflow page */
int ovflSize; /* Bytes of data per overflow page. */
@@ -6908,6 +6964,16 @@ int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, const void *z){
if( pInfo->nData<(offset+amt) ){
return SQLITE_ERROR;
}
ovflSize = pBt->usableSize - 4;
assert(pCsr->cacheOverflow);
if( !pCsr->aOverflow ){
int nOverflow = (pInfo->nPayload - pInfo->nLocal + ovflSize - 1)/ovflSize;
pCsr->aOverflow = (Pgno *)sqliteMalloc(sizeof(Pgno)*nOverflow);
if( nOverflow && !pCsr->aOverflow ){
return SQLITE_NOMEM;
}
}
if( pInfo->nLocal>iOffset ){
/* In this case data must be written to the b-tree page. */
@@ -6926,50 +6992,69 @@ int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, const void *z){
}
iOffset = ((iOffset<pInfo->nLocal)?0:(iOffset-pInfo->nLocal));
ovflSize = pBt->usableSize - 4;
assert(pInfo->iOverflow>0 || iRem==0);
iOvfl = get4byte(&pInfo->pCell[pInfo->iOverflow]);
while( iRem>0 ){
if( iOffset>ovflSize ){
/* The only reason to read this page is to obtain the page
** number for the next page in the overflow chain. So try
** the getOverflowPage() shortcut. */
rc = getOverflowPage(pBt, iOvfl, 0, &iOvfl);
if( rc!=SQLITE_OK ){
return rc;
}
iOffset -= ovflSize;
if( iRem>0 ){
if( pCsr->aOverflow[iOffset/ovflSize] ){
iIdx = iOffset/ovflSize;
iOvfl = pCsr->aOverflow[iIdx];
iOffset = iOffset%ovflSize;
}else{
int iWrite = ovflSize - iOffset;
DbPage *pOvfl; /* The overflow page. */
u8 *aData; /* Page data */
rc = sqlite3PagerGet(pBt->pPager, iOvfl, &pOvfl);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pOvfl);
if( rc!=SQLITE_OK ){
iOvfl = get4byte(&pInfo->pCell[pInfo->iOverflow]);
}
for(iIdx++; iRem>0; iIdx++){
if( iOffset>ovflSize ){
/* The only reason to read this page is to obtain the page
** number for the next page in the overflow chain. So try
** the getOverflowPage() shortcut. */
rc = getOverflowPage(pBt, iOvfl, 0, &iOvfl);
if( rc!=SQLITE_OK ){
return rc;
}
iOffset -= ovflSize;
pCsr->aOverflow[iIdx] = iOvfl;
}else{
int iWrite = ovflSize - iOffset;
DbPage *pOvfl; /* The overflow page. */
u8 *aData; /* Page data */
rc = sqlite3PagerGet(pBt->pPager, iOvfl, &pOvfl);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pOvfl);
if( rc!=SQLITE_OK ){
sqlite3PagerUnref(pOvfl);
return rc;
}
aData = sqlite3PagerGetData(pOvfl);
iOvfl = get4byte(aData);
pCsr->aOverflow[iIdx] = iOvfl;
if( iWrite>iRem ){
iWrite = iRem;
}
memcpy(&aData[iOffset+4], zRem, iWrite);
sqlite3PagerUnref(pOvfl);
return rc;
zRem += iWrite;
iRem -= iWrite;
iOffset = ((iOffset<ovflSize)?0:(iOffset-ovflSize));
}
aData = sqlite3PagerGetData(pOvfl);
iOvfl = get4byte(aData);
if( iWrite>iRem ){
iWrite = iRem;
}
memcpy(&aData[iOffset+4], zRem, iWrite);
sqlite3PagerUnref(pOvfl);
zRem += iWrite;
iRem -= iWrite;
iOffset = ((iOffset<ovflSize)?0:(iOffset-ovflSize));
}
}
return SQLITE_OK;
}
/*
** Set a flag on this cursor to cache the locations of pages from the
** overflow list for the current row.
*/
void sqlite3BtreeCacheOverflow(BtCursor *pCur){
assert(!pCur->cacheOverflow);
assert(!pCur->aOverflow);
pCur->cacheOverflow = 1;
}
#endif
/*