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Avoid unnecessary calls to balance() from sqlite3BtreeDelete().

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FossilOrigin-Name: d0966d1bdd474e27cb048884d340184f0e81a4fab65eb6b74682b20630caddf8
This commit is contained in:
drh
2022-03-29 13:16:32 +00:00
parent fb92e07186
commit de9484858e
3 changed files with 21 additions and 10 deletions
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17
src/btree.c
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@@ -8742,7 +8742,6 @@ static int anotherValidCursor(BtCursor *pCur){
*/
static int balance(BtCursor *pCur){
int rc = SQLITE_OK;
const int nMin = pCur->pBt->usableSize * 2 / 3;
u8 aBalanceQuickSpace[13];
u8 *pFree = 0;
@@ -8754,7 +8753,11 @@ static int balance(BtCursor *pCur){
MemPage *pPage = pCur->pPage;
if( NEVER(pPage->nFree<0) && btreeComputeFreeSpace(pPage) ) break;
if( pPage->nOverflow==0 && pPage->nFree<=nMin ){
if( pPage->nOverflow==0 && pPage->nFree*3<=pCur->pBt->usableSize*2 ){
/* No rebalance required as long as:
** (1) There are no overflow cells
** (2) The amount of free space on the page is less than 2/3rds of
** the total usable space on the page. */
break;
}else if( (iPage = pCur->iPage)==0 ){
if( pPage->nOverflow && (rc = anotherValidCursor(pCur))==SQLITE_OK ){
@@ -9568,7 +9571,15 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
** been corrected, so be it. Otherwise, after balancing the leaf node,
** walk the cursor up the tree to the internal node and balance it as
** well. */
rc = balance(pCur);
assert( pCur->pPage->nOverflow==0 );
assert( pCur->pPage->nFree>=0 );
if( pCur->pPage->nFree*3<=pCur->pBt->usableSize*2 ){
/* Optimization: If the free space is less than 2/3rds of the page,
** then balance() will always be a no-op. No need to invoke it. */
rc = SQLITE_OK;
}else{
rc = balance(pCur);
}
if( rc==SQLITE_OK && pCur->iPage>iCellDepth ){
releasePageNotNull(pCur->pPage);
pCur->iPage--;