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Further optimizations to the UPDATE logic to avoid making changes to partial

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indexes if none of the columns mentioned in the WHERE clause are modified by
the UPDATE.

FossilOrigin-Name: d1365a5bf0ee2f145427b81d2a593f539c3ad4705d579478703c1f65ae5f80bf
This commit is contained in:
drh
2018-09-17 20:47:38 +00:00
parent d4cb09e3d2
commit 40b4e7a692
3 changed files with 35 additions and 9 deletions
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30
src/update.c
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@@ -82,7 +82,9 @@ void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i, int iReg){
/*
** Check to see if column iCol of index pIdx references any of the
** columns defined by aXRef and chngRowid. Return true if it does
** and false if not.
** and false if not. This is an optimization. False-positives are a
** performance degradation, but false-negatives can result in a corrupt
** index and incorrect answers.
**
** aXRef[j] will be non-negative if column j of the original table is
** being updated. chngRowid will be true if the rowid of the table is
@@ -106,6 +108,28 @@ static int indexColumnIsBeingUpdated(
aXRef,chngRowid);
}
/*
** Check to see if index pIdx is a partial index whose conditional
** expression might change values due to an UPDATE. Return true if
** the index is subject to change and false if the index is guaranteed
** to be unchanged. This is an optimization. False-positives are a
** performance degradation, but false-negatives can result in a corrupt
** index and incorrect answers.
**
** aXRef[j] will be non-negative if column j of the original table is
** being updated. chngRowid will be true if the rowid of the table is
** being updated.
*/
static int indexWhereClauseMightChange(
Index *pIdx, /* The index to check */
int *aXRef, /* aXRef[j]>=0 if column j is being updated */
int chngRowid /* true if the rowid is being updated */
){
if( pIdx->pPartIdxWhere==0 ) return 0;
return sqlite3ExprReferencesUpdatedColumn(pIdx->pPartIdxWhere,
aXRef, chngRowid);
}
/*
** Process an UPDATE statement.
**
@@ -332,7 +356,9 @@ void sqlite3Update(
*/
for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
int reg;
if( chngKey || hasFK>1 || pIdx->pPartIdxWhere || pIdx==pPk ){
if( chngKey || hasFK>1 || pIdx==pPk
|| indexWhereClauseMightChange(pIdx,aXRef,chngRowid)
){
reg = ++pParse->nMem;
pParse->nMem += pIdx->nColumn;
}else{