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Make the sqlite3BtreeMoveto routine a no-op if the cursor is already pointing

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at the cell we are trying to move to. (CVS 4938)

FossilOrigin-Name: 9b567ab61e7542141b7bc9c3c053c2d1180da92d
This commit is contained in:
drh
2008-03-29 16:01:04 +00:00
parent 907b46ca16
commit a2c20e433b
4 changed files with 46 additions and 12 deletions
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36
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 1.447 2008/03/25 17:23:33 drh Exp $
** $Id: btree.c,v 1.448 2008/03/29 16:01:04 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
@@ -2847,6 +2847,7 @@ void sqlite3BtreeReleaseTempCursor(BtCursor *pCur){
static void getCellInfo(BtCursor *pCur){
if( pCur->info.nSize==0 ){
sqlite3BtreeParseCell(pCur->pPage, pCur->idx, &pCur->info);
pCur->validNKey = 1;
}else{
assertCellInfo(pCur);
}
@@ -2856,6 +2857,7 @@ void sqlite3BtreeReleaseTempCursor(BtCursor *pCur){
#define getCellInfo(pCur) \
if( pCur->info.nSize==0 ){ \
sqlite3BtreeParseCell(pCur->pPage, pCur->idx, &pCur->info); \
pCur->validNKey = 1; \
}else{ \
assertCellInfo(pCur); \
}
@@ -3349,6 +3351,7 @@ static int moveToChild(BtCursor *pCur, u32 newPgno){
pCur->pPage = pNewPage;
pCur->idx = 0;
pCur->info.nSize = 0;
pCur->validNKey = 0;
if( pNewPage->nCell<1 ){
return SQLITE_CORRUPT_BKPT;
}
@@ -3400,6 +3403,7 @@ void sqlite3BtreeMoveToParent(BtCursor *pCur){
releasePage(pPage);
pCur->pPage = pParent;
pCur->info.nSize = 0;
pCur->validNKey = 0;
assert( pParent->idxShift==0 );
pCur->idx = idxParent;
}
@@ -3438,6 +3442,8 @@ static int moveToRoot(BtCursor *pCur){
}
pCur->idx = 0;
pCur->info.nSize = 0;
pCur->atLast = 0;
pCur->validNKey = 0;
if( pRoot->nCell==0 && !pRoot->leaf ){
Pgno subpage;
assert( pRoot->pgno==1 );
@@ -3497,6 +3503,7 @@ static int moveToRightmost(BtCursor *pCur){
if( rc==SQLITE_OK ){
pCur->idx = pPage->nCell - 1;
pCur->info.nSize = 0;
pCur->validNKey = 0;
}
return SQLITE_OK;
}
@@ -3543,6 +3550,8 @@ int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
assert( pCur->eState==CURSOR_VALID );
*pRes = 0;
rc = moveToRightmost(pCur);
getCellInfo(pCur);
pCur->atLast = rc==SQLITE_OK;
}
}
return rc;
@@ -3589,6 +3598,21 @@ int sqlite3BtreeMoveto(
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;
@@ -3638,6 +3662,7 @@ int sqlite3BtreeMoveto(
void *pCellKey;
i64 nCellKey;
pCur->info.nSize = 0;
pCur->validNKey = 1;
if( pPage->intKey ){
u8 *pCell;
pCell = findCell(pPage, pCur->idx) + pPage->childPtrSize;
@@ -3645,7 +3670,7 @@ int sqlite3BtreeMoveto(
u32 dummy;
pCell += getVarint32(pCell, &dummy);
}
getVarint(pCell, (u64 *)&nCellKey);
getVarint(pCell, (u64*)&nCellKey);
if( nCellKey<nKey ){
c = -1;
}else if( nCellKey>nKey ){
@@ -3672,6 +3697,7 @@ int sqlite3BtreeMoveto(
}
}
if( c==0 ){
pCur->info.nKey = nCellKey;
if( pPage->leafData && !pPage->leaf ){
lwr = pCur->idx;
upr = lwr - 1;
@@ -3688,6 +3714,7 @@ int sqlite3BtreeMoveto(
upr = pCur->idx-1;
}
if( lwr>upr ){
pCur->info.nKey = nCellKey;
break;
}
pCur->idx = (lwr+upr)/2;
@@ -3709,6 +3736,7 @@ int sqlite3BtreeMoveto(
}
pCur->idx = lwr;
pCur->info.nSize = 0;
pCur->validNKey = 0;
rc = moveToChild(pCur, chldPg);
if( rc ) goto moveto_finish;
}
@@ -3778,6 +3806,7 @@ static int btreeNext(BtCursor *pCur, int *pRes){
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]));
@@ -3834,6 +3863,7 @@ static int btreePrevious(BtCursor *pCur, int *pRes){
if( rc!=SQLITE_OK ){
return rc;
}
pCur->atLast = 0;
if( CURSOR_INVALID==pCur->eState ){
*pRes = 1;
return SQLITE_OK;
@@ -3867,6 +3897,7 @@ static int btreePrevious(BtCursor *pCur, int *pRes){
}
pCur->idx--;
pCur->info.nSize = 0;
pCur->validNKey = 0;
if( pPage->leafData && !pPage->leaf ){
rc = sqlite3BtreePrevious(pCur, pRes);
}else{
@@ -5673,6 +5704,7 @@ int sqlite3BtreeInsert(
assert( pPage->leaf );
pCur->idx++;
pCur->info.nSize = 0;
pCur->validNKey = 0;
}else{
assert( pPage->leaf );
}