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First cut at optimizing single-row updates to use a one-pass algorithm. (CVS 4973)

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FossilOrigin-Name: fba97f7874d723111e873d1470fc1a95e64f922d
This commit is contained in:
drh
2008-04-10 13:33:18 +00:00
parent 67ade0a2d0
commit 08c88eb0d3
7 changed files with 68 additions and 40 deletions
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26
src/where.c
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@@ -16,7 +16,7 @@
** so is applicable. Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.297 2008/04/01 05:07:15 drh Exp $
** $Id: where.c,v 1.298 2008/04/10 13:33:18 drh Exp $
*/
#include "sqliteInt.h"
@@ -2002,7 +2002,7 @@ WhereInfo *sqlite3WhereBegin(
SrcList *pTabList, /* A list of all tables to be scanned */
Expr *pWhere, /* The WHERE clause */
ExprList **ppOrderBy, /* An ORDER BY clause, or NULL */
u8 obflag /* One of ORDERBY_MIN, ORDERBY_MAX or ORDERBY_NORMAL */
u8 wflags /* One of the WHERE_* flags defined in sqliteInt.h */
){
int i; /* Loop counter */
WhereInfo *pWInfo; /* Will become the return value of this function */
@@ -2210,6 +2210,17 @@ WhereInfo *sqlite3WhereBegin(
*ppOrderBy = 0;
}
/* If the caller is an UPDATE or DELETE statement that is requesting
** to use a one-pass algorithm, determine if this is appropriate.
** The one-pass algorithm only works if the WHERE clause constraints
** the statement to update a single row.
*/
assert( (wflags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
if( (wflags & WHERE_ONEPASS_DESIRED)!=0 && (andFlags & WHERE_UNIQUE)!=0 ){
pWInfo->okOnePass = 1;
pWInfo->a[0].flags &= ~WHERE_IDX_ONLY;
}
/* Open all tables in the pTabList and any indices selected for
** searching those tables.
*/
@@ -2258,8 +2269,9 @@ WhereInfo *sqlite3WhereBegin(
}else
#endif
if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, OP_OpenRead);
if( pTab->nCol<(sizeof(Bitmask)*8) ){
int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
if( !pWInfo->okOnePass && pTab->nCol<(sizeof(Bitmask)*8) ){
Bitmask b = pTabItem->colUsed;
int n = 0;
for(; b; b=b>>1, n++){}
@@ -2496,7 +2508,7 @@ WhereInfo *sqlite3WhereBegin(
** the first one after the nEq equality constraints in the index,
** this requires some special handling.
*/
if( (obflag==ORDERBY_MIN)
if( (wflags&WHERE_ORDERBY_MIN)!=0
&& (pLevel->flags&WHERE_ORDERBY)
&& (pIdx->nColumn>nEq)
&& (pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq])
@@ -2635,7 +2647,7 @@ WhereInfo *sqlite3WhereBegin(
regBase = codeAllEqualityTerms(pParse, pLevel, &wc, notReady, 1);
nxt = pLevel->nxt;
if( (obflag==ORDERBY_MIN)
if( (wflags&WHERE_ORDERBY_MIN)!=0
&& (pLevel->flags&WHERE_ORDERBY)
&& (pIdx->nColumn>nEq)
&& (pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq])
@@ -2853,7 +2865,7 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
Table *pTab = pTabItem->pTab;
assert( pTab!=0 );
if( pTab->isEphem || pTab->pSelect ) continue;
if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
if( !pWInfo->okOnePass && (pLevel->flags & WHERE_IDX_ONLY)==0 ){
sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
}
if( pLevel->pIdx!=0 ){