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Multiply all cursor step cost estimates by the estimated size of the row in

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bytes, in order to get the query planner ot make use of estimated row sizes.
This check-in uses magic numbers in a few places (for example, estimates of
the size of output rows) and needs lots of refinement.  Consider this a
proof-of-concept only.

FossilOrigin-Name: cb34cfe57c2a664fbfae8106e95114400ea222d5
This commit is contained in:
drh
2013-10-07 17:32:15 +00:00
parent 6f38a6418c
commit 3495d20dbe
3 changed files with 19 additions and 15 deletions
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20
src/where.c
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@@ -4368,7 +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);
pNew->rRun = sqlite3LogEstAdd(pNew->rRun, pNew->nOut) + pProbe->szIdxRow;
whereLoopOutputAdjust(pBuilder->pWC, pNew, pSrc->iCursor);
rc = whereLoopInsert(pBuilder, pNew);
if( (pNew->wsFlags & WHERE_TOP_LIMIT)==0
@@ -4471,11 +4471,13 @@ static int whereLoopAddBtree(
LogEst rSize; /* number of rows in the table */
LogEst rLogSize; /* Logarithm of the number of rows in the table */
WhereClause *pWC; /* The parsed WHERE clause */
Table *pTab; /* Table being queried */
pNew = pBuilder->pNew;
pWInfo = pBuilder->pWInfo;
pTabList = pWInfo->pTabList;
pSrc = pTabList->a + pNew->iTab;
pTab = pSrc->pTab;
pWC = pBuilder->pWC;
assert( !IsVirtual(pSrc->pTab) );
@@ -4493,8 +4495,8 @@ static int whereLoopAddBtree(
sPk.aiColumn = &aiColumnPk;
sPk.aiRowEst = aiRowEstPk;
sPk.onError = OE_Replace;
sPk.pTable = pSrc->pTab;
aiRowEstPk[0] = pSrc->pTab->nRowEst;
sPk.pTable = pTab;
aiRowEstPk[0] = pTab->nRowEst;
aiRowEstPk[1] = 1;
pFirst = pSrc->pTab->pIndex;
if( pSrc->notIndexed==0 ){
@@ -4504,7 +4506,7 @@ static int whereLoopAddBtree(
}
pProbe = &sPk;
}
rSize = sqlite3LogEst(pSrc->pTab->nRowEst);
rSize = sqlite3LogEst(pTab->nRowEst);
rLogSize = estLog(rSize);
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
@@ -4530,12 +4532,13 @@ 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);
pNew->rRun = sqlite3LogEstAdd(rLogSize,pNew->nOut) + pTab->szTabRow;
pNew->wsFlags = WHERE_AUTO_INDEX;
pNew->prereq = mExtra | pTerm->prereqRight;
rc = whereLoopInsert(pBuilder, pNew);
@@ -4570,7 +4573,7 @@ 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;
pNew->rRun = sqlite3LogEstAdd(rSize,rLogSize) + 16 + pTab->szTabRow;
whereLoopOutputAdjust(pWC, pNew, pSrc->iCursor);
rc = whereLoopInsert(pBuilder, pNew);
pNew->nOut = rSize;
@@ -4602,6 +4605,7 @@ static int whereLoopAddBtree(
** 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;
@@ -4773,7 +4777,7 @@ static int whereLoopAddVirtual(
pNew->u.vtab.isOrdered = (u8)((pIdxInfo->nOrderBy!=0)
&& pIdxInfo->orderByConsumed);
pNew->rSetup = 0;
pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost) + 55;
/* TUNING: Every virtual table query returns 25 rows */
pNew->nOut = 46; assert( 46==sqlite3LogEst(25) );
whereLoopInsert(pBuilder, pNew);
@@ -5264,7 +5268,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
}else{
/* TUNING: Estimated cost of sorting is N*log2(N) where N is the
** number of output rows. */
rSortCost = nRowEst + estLog(nRowEst);
rSortCost = nRowEst + estLog(nRowEst) + 55;
WHERETRACE(0x002,("---- sort cost=%-3d\n", rSortCost));
}