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Disable the table selection rule that tried to prevent full table scans from

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migrating to the outer loop unless they were optimal.  The new scaling of 
outer-loop costs by cost of inner loops obviates the need for that step.  And,
in fact, that step causes problems with the new inner-loop cost accounting.

FossilOrigin-Name: 51bfd63b7f9fe53831570ad124c932cb3582b104
This commit is contained in:
drh
2012-11-09 18:22:26 +00:00
parent 782d68a4cd
commit ada796bbaa
3 changed files with 9 additions and 25 deletions
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17
src/where.c
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@@ -4744,16 +4744,6 @@ static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
}
}
/*
** Return TRUE if the wsFlags indicate that a full table scan (or a
** full scan of a covering index) is indicated.
*/
static int isFullscan(unsigned wsFlags){
if( wsFlags & WHERE_COVER_SCAN ) return 1;
if( (wsFlags & WHERE_NOT_FULLSCAN)==0 ) return 1;
return 0;
}
/*
** Generate the beginning of the loop used for WHERE clause processing.
@@ -5132,8 +5122,8 @@ WhereInfo *sqlite3WhereBegin(
** yet run. (In other words, it must not depend on tables
** in inner loops.)
**
** (2) A full-table-scan plan cannot supercede indexed plan unless
** the full-table-scan is an "optimal" plan as defined above.
** (2) (This rule was removed on 2012-11-09. The scaling of the
** cost using the optimal scan cost made this rule obsolete.)
**
** (3) All tables have an INDEXED BY clause or this table lacks an
** INDEXED BY clause or this table uses the specific
@@ -5148,9 +5138,6 @@ WhereInfo *sqlite3WhereBegin(
** is defined by the compareCost() function above.
*/
if( (sWBI.cost.used&sWBI.notValid)==0 /* (1) */
&& (bestJ<0 || (notIndexed&m)!=0 /* (2) */
|| isFullscan(bestPlan.plan.wsFlags)
|| !isFullscan(sWBI.cost.plan.wsFlags))
&& (nUnconstrained==0 || sWBI.pSrc->pIndex==0 /* (3) */
|| NEVER((sWBI.cost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0))
&& (bestJ<0 || compareCost(&sWBI.cost, &bestPlan)) /* (4) */