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Progress toward using the iScanRatio information on indices. Many tests

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are still failing.

FossilOrigin-Name: 6c352edbba85a15ca356b5e131f4b3b2723d1774
This commit is contained in:
drh
2013-10-04 02:36:19 +00:00
parent c28c4e5009
commit d9e3cad2f8
7 changed files with 52 additions and 57 deletions
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22
src/where.c
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@@ -4669,10 +4669,8 @@ static int whereLoopAddBtree(
/* Full table scan */
pNew->iSortIdx = b ? iSortIdx : 0;
/* TUNING: Cost of full table scan is 3*(N + log2(N)).
** + The extra 3 factor is to encourage the use of indexed lookups
** over full scans. A smaller constant 2 is used for covering
** index scans so that a covering index scan will be favored over
** a table scan. */
** + The extra 4 factor is to encourage the use of indexed lookups
** over full scans. */
pNew->rRun = whereCostAdd(rSize,rLogSize) + 16;
whereLoopOutputAdjust(pWC, pNew, pSrc->iCursor);
rc = whereLoopInsert(pBuilder, pNew);
@@ -4686,6 +4684,7 @@ static int whereLoopAddBtree(
if( b
|| ( m==0
&& pProbe->bUnordered==0
&& pProbe->iScanRatio<128
&& (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0
&& sqlite3GlobalConfig.bUseCis
&& OptimizationEnabled(pWInfo->pParse->db, SQLITE_CoverIdxScan)
@@ -4693,15 +4692,12 @@ static int whereLoopAddBtree(
){
pNew->iSortIdx = b ? iSortIdx : 0;
if( m==0 ){
/* TUNING: Cost of a covering index scan is 2*(N + log2(N)).
** + The extra 2 factor is to encourage the use of indexed lookups
** over index scans. A table scan uses a factor of 3 so that
** index scans are favored over table scans.
** + If this covering index might also help satisfy the ORDER BY
** clause, then the cost is fudged down slightly so that this
** index is favored above other indices that have no hope of
** helping with the ORDER BY. */
pNew->rRun = 10 + whereCostAdd(rSize,rLogSize) - b;
/* TUNING: Cost of a covering index scan is K*(N + log2(N)).
** + The extra factor K of between 1.0 and 3.0 is added to
** encourage the use of indexed lookups. The value of K
** depends on the iScanRatio value for the index.
*/
pNew->rRun = whereCostAdd(rSize,rLogSize) + pProbe->iScanRatio/9 + 1;
}else{
assert( b!=0 );
/* TUNING: Cost of scanning a non-covering index is (N+1)*log2(N)