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Rollback some of the previous changes in the branch such that the estimated

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row sizes are now only used as a tie-breaker for index scans.

FossilOrigin-Name: 65553ff34b41e54d129ff2fee96be714105503c4
This commit is contained in:
drh
2013-10-08 20:42:41 +00:00
parent 5f3e5e747d
commit b50596d64d
5 changed files with 42 additions and 28 deletions
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28
src/where.c
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@@ -4338,12 +4338,6 @@ static int whereLoopAddBtreeIndex(
/* Adjust nOut and rRun for STAT3 range values */
assert( pNew->nOut==saved_nOut );
whereRangeScanEst(pParse, pBuilder, pBtm, pTop, pNew);
/* If the range constraint is the only constraint on the index and
** if the range constraint does not reduce the search space,
** then this is really just an index scan which has already
** been analyzed. */
if( pNew->nOut>=saved_nOut && pNew->u.btree.nEq==0 ) continue;
}
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
if( nInMul==0
@@ -4374,7 +4368,7 @@ static int whereLoopAddBtreeIndex(
pNew->rRun = sqlite3LogEstAdd(pNew->rRun,rLogSize>27 ? rLogSize-17 : 10);
}
/* Step cost for each output row */
pNew->rRun = sqlite3LogEstAdd(pNew->rRun, pNew->nOut) + pProbe->szIdxRow;
pNew->rRun = sqlite3LogEstAdd(pNew->rRun, pNew->nOut);
whereLoopOutputAdjust(pBuilder->pWC, pNew, pSrc->iCursor);
rc = whereLoopInsert(pBuilder, pNew);
if( (pNew->wsFlags & WHERE_TOP_LIMIT)==0
@@ -4538,13 +4532,12 @@ static int whereLoopAddBtree(
** approximately 7*N*log2(N) where N is the number of rows in
** the table being indexed. */
pNew->rSetup = rLogSize + rSize + 28; assert( 28==sqlite3LogEst(7) );
pNew->rSetup += pTab->szTabRow;
/* TUNING: Each index lookup yields 20 rows in the table. This
** is more than the usual guess of 10 rows, since we have no way
** of knowning how selective the index will ultimately be. It would
** not be unreasonable to make this value much larger. */
pNew->nOut = 43; assert( 43==sqlite3LogEst(20) );
pNew->rRun = sqlite3LogEstAdd(rLogSize,pNew->nOut) + pTab->szTabRow;
pNew->rRun = sqlite3LogEstAdd(rLogSize,pNew->nOut);
pNew->wsFlags = WHERE_AUTO_INDEX;
pNew->prereq = mExtra | pTerm->prereqRight;
rc = whereLoopInsert(pBuilder, pNew);
@@ -4579,7 +4572,7 @@ static int whereLoopAddBtree(
/* 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. FIXME */
pNew->rRun = sqlite3LogEstAdd(rSize,rLogSize) + 16 + pTab->szTabRow;
pNew->rRun = sqlite3LogEstAdd(rSize,rLogSize) + 16;
whereLoopOutputAdjust(pWC, pNew, pSrc->iCursor);
rc = whereLoopInsert(pBuilder, pNew);
pNew->nOut = rSize;
@@ -4592,6 +4585,7 @@ static int whereLoopAddBtree(
if( b
|| ( m==0
&& pProbe->bUnordered==0
&& pProbe->szIdxRow<pTab->szTabRow
&& (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0
&& sqlite3GlobalConfig.bUseCis
&& OptimizationEnabled(pWInfo->pParse->db, SQLITE_CoverIdxScan)
@@ -4600,18 +4594,18 @@ static int whereLoopAddBtree(
pNew->iSortIdx = b ? iSortIdx : 0;
if( m==0 ){
/* TUNING: Cost of a covering index scan is K*(N + log2(N)).
** + The extra factor K of between 1.1 (iScanRatio between 0
** and 9) and 2.8 (iScanRatio between 126 and 127) is added
** to encourage the use of indexed lookups. FIXME
** + The extra factor K of between 1.1 and 3.0 that depends
** on the relative sizes of the table and the index. K
** is smaller for smaller indices, thus favoring them.
*/
pNew->rRun = sqlite3LogEstAdd(rSize,rLogSize) + 10;
pNew->rRun = sqlite3LogEstAdd(rSize,rLogSize) + 1 +
(15*pProbe->szIdxRow)/pTab->szTabRow;
}else{
assert( b!=0 );
/* TUNING: Cost of scanning a non-covering index is (N+1)*log2(N)
** which we will simplify to just N*log2(N) */
pNew->rRun = rSize + rLogSize;
}
pNew->rRun += pProbe->szIdxRow;
whereLoopOutputAdjust(pWC, pNew, pSrc->iCursor);
rc = whereLoopInsert(pBuilder, pNew);
pNew->nOut = rSize;
@@ -4783,7 +4777,7 @@ static int whereLoopAddVirtual(
pNew->u.vtab.isOrdered = (u8)((pIdxInfo->nOrderBy!=0)
&& pIdxInfo->orderByConsumed);
pNew->rSetup = 0;
pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost) + 55;
pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
/* TUNING: Every virtual table query returns 25 rows */
pNew->nOut = 46; assert( 46==sqlite3LogEst(25) );
whereLoopInsert(pBuilder, pNew);
@@ -5276,7 +5270,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
** number of output rows. The 48 is the expected size of a row to sort.
** FIXME: compute a better estimate of the 48 multiplier based on the
** result set expressions. */
rSortCost = nRowEst + estLog(nRowEst) + 55;
rSortCost = nRowEst + estLog(nRowEst);
WHERETRACE(0x002,("---- sort cost=%-3d\n", rSortCost));
}