Make use of histogram data to make better estimates for the number of rows
that will be returned from "x IN (v1,v2,v3,...)" constraints. FossilOrigin-Name: fd3977a27ae68e694df12a4713e55515c1e87c5d
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drh
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18
manifest
@ -1,8 +1,8 @@
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-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA1
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C Add\sthe\sability\sto\suse\sindices\swhen\sa\srange\scontraint\sis\sbounded\son\nthe\slower\send\sby\sNULL.
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D 2011-01-21T14:37:04.663
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C Make\suse\sof\shistogram\sdata\sto\smake\sbetter\sestimates\sfor\sthe\snumber\sof\srows\nthat\swill\sbe\sreturned\sfrom\s"x\sIN\s(v1,v2,v3,...)"\sconstraints.
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D 2011-01-21T16:27:18.621
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F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
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F Makefile.in de6498556d536ae60bb8bb10e8c1ba011448658c
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F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
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@ -243,7 +243,7 @@ F src/vtab.c b297e8fa656ab5e66244ab15680d68db0adbec30
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F src/wal.c dbca424f71678f663a286ab2a98f947af1d412a7
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F src/wal.h c1aac6593a0b02b15dc625987e619edeab39292e
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F src/walker.c 3112bb3afe1d85dc52317cb1d752055e9a781f8f
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F src/where.c cf219a4275cf430d0e7df9d2db04e9ba29702f8e
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F src/where.c 7f2844afffd9e09373e874a74de81d3502b2a35c
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F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
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F test/alias.test 4529fbc152f190268a15f9384a5651bbbabc9d87
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F test/all.test 51756962d522e474338e9b2ebb26e7364d4aa125
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@ -900,14 +900,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
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F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
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F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
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F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
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P c7b59afaf0c0bf85dbaf0a122cc8d65fca93680f
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R 07d2f363ee58370384294fd182ee30ff
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P f73a167b434fadcbbd15e3891c4b7f4f87f6363c
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R 46f7d508c889f9891a64638b5f1737ae
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U drh
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Z 32ed47abc5f3838cb9feba0ba8b99416
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Z 14ba122ed035896c7c1b08aa324c4833
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@ -1 +1 @@
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f73a167b434fadcbbd15e3891c4b7f4f87f6363c
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fd3977a27ae68e694df12a4713e55515c1e87c5d
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103
src/where.c
103
src/where.c
@ -2475,18 +2475,19 @@ range_est_fallback:
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** column of an index and sqlite_stat2 histogram data is available
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** for that index.
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**
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** Write the estimated row count into *pnRow. If unable to make
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** an estimate, leave *pnRow unchanged.
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** Write the estimated row count into *pnRow and return SQLITE_OK.
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** If unable to make an estimate, leave *pnRow unchanged and return
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** non-zero.
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**
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** This routine can fail if it is unable to load a collating sequence
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** required for string comparison, or if unable to allocate memory
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** for a UTF conversion required for comparison. The error is stored
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** in the pParse structure.
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*/
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void whereEqScanEst(
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int whereEqualScanEst(
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Parse *pParse, /* Parsing & code generating context */
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Index *p, /* The index whose left-most column is pTerm */
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WhereTerm *pTerm, /* The x=VALUE constraint */
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Expr *pExpr, /* Expression for VALUE in the x=VALUE constraint */
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double *pnRow /* Write the revised row estimate here */
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){
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sqlite3_value *pRhs = 0; /* VALUE on right-hand side of pTerm */
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@ -2496,14 +2497,14 @@ void whereEqScanEst(
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double nRowEst; /* New estimate of the number of rows */
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assert( p->aSample!=0 );
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assert( pTerm->eOperator==WO_EQ );
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aff = p->pTable->aCol[p->aiColumn[0]].affinity;
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rc = valueFromExpr(pParse, pTerm->pExpr->pRight, aff, &pRhs);
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if( rc ) goto whereEqScanEst_cancel;
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rc = valueFromExpr(pParse, pExpr, aff, &pRhs);
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if( rc ) goto whereEqualScanEst_cancel;
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if( pRhs==0 ) return SQLITE_NOTFOUND;
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rc = whereRangeRegion(pParse, p, pRhs, 0, &iLower);
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if( rc ) goto whereEqScanEst_cancel;
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if( rc ) goto whereEqualScanEst_cancel;
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rc = whereRangeRegion(pParse, p, pRhs, 1, &iUpper);
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if( rc ) goto whereEqScanEst_cancel;
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if( rc ) goto whereEqualScanEst_cancel;
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WHERETRACE(("equality scan regions: %d..%d\n", iLower, iUpper));
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if( iLower>=iUpper ){
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nRowEst = p->aiRowEst[0]/(SQLITE_INDEX_SAMPLES*2);
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@ -2513,8 +2514,76 @@ void whereEqScanEst(
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*pnRow = nRowEst;
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}
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whereEqScanEst_cancel:
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whereEqualScanEst_cancel:
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sqlite3ValueFree(pRhs);
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return rc;
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}
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#endif /* defined(SQLITE_ENABLE_STAT2) */
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#ifdef SQLITE_ENABLE_STAT2
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/*
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** Estimate the number of rows that will be returned based on
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** an IN constraint "x IN (V1,V2,V3,...)" where the right-hand side
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** of the IN operator is a list of values.
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**
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** Write the estimated row count into *pnRow and return SQLITE_OK.
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** If unable to make an estimate, leave *pnRow unchanged and return
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** non-zero.
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**
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** This routine can fail if it is unable to load a collating sequence
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** required for string comparison, or if unable to allocate memory
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** for a UTF conversion required for comparison. The error is stored
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** in the pParse structure.
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*/
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int whereInScanEst(
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Parse *pParse, /* Parsing & code generating context */
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Index *p, /* The index whose left-most column is pTerm */
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ExprList *pList, /* The value list on the RHS of "x IN (v1,v2,v3,...)" */
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double *pnRow /* Write the revised row estimate here */
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){
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sqlite3_value *pVal = 0; /* One value from list */
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int iLower, iUpper; /* Range of histogram regions containing pRhs */
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u8 aff; /* Column affinity */
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int rc; /* Subfunction return code */
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double nRowEst; /* New estimate of the number of rows */
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int nRegion = 0; /* Number of histogram regions spanned */
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int nSingle = 0; /* Count of values contained within one region */
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int nNotFound = 0; /* Count of values that are not constants */
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int i; /* Loop counter */
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u8 aHit[SQLITE_INDEX_SAMPLES+1]; /* Histogram regions that are spanned */
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assert( p->aSample!=0 );
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aff = p->pTable->aCol[p->aiColumn[0]].affinity;
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memset(aHit, 0, sizeof(aHit));
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for(i=0; i<pList->nExpr; i++){
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sqlite3ValueFree(pVal);
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rc = valueFromExpr(pParse, pList->a[i].pExpr, aff, &pVal);
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if( rc ) break;
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if( pVal==0 ){
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nNotFound++;
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continue;
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}
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rc = whereRangeRegion(pParse, p, pVal, 0, &iLower);
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if( rc ) break;
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rc = whereRangeRegion(pParse, p, pVal, 1, &iUpper);
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if( rc ) break;
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if( iLower>=iUpper ){
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nSingle++;
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}
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assert( iLower>=0 && iUpper<=SQLITE_INDEX_SAMPLES );
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while( iLower<=iUpper ) aHit[iLower++] = 1;
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}
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if( rc==SQLITE_OK ){
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for(i=nRegion=0; i<ArraySize(aHit); i++) nRegion += aHit[i];
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nRowEst = nRegion*p->aiRowEst[0]/(SQLITE_INDEX_SAMPLES+1)
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+ nNotFound*p->aiRowEst[1];
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if( nRowEst > p->aiRowEst[0] ) nRowEst = p->aiRowEst[0];
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*pnRow = nRowEst;
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WHERETRACE(("IN row estimate: nRegion=%d, nSingle=%d, nNotFound=%d\n",
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nRegion, nSingle, nNotFound));
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}
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sqlite3ValueFree(pVal);
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return rc;
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}
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#endif /* defined(SQLITE_ENABLE_STAT2) */
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@ -2686,7 +2755,7 @@ static void bestBtreeIndex(
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int bLookup = 0;
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WhereTerm *pTerm; /* A single term of the WHERE clause */
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#ifdef SQLITE_ENABLE_STAT2
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WhereTerm *pFirstEqTerm = 0; /* First WO_EQ term */
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WhereTerm *pFirstTerm = 0; /* First term matching the index */
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#endif
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/* Determine the values of nEq and nInMul */
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@ -2710,9 +2779,7 @@ static void bestBtreeIndex(
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wsFlags |= WHERE_COLUMN_NULL;
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}
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#ifdef SQLITE_ENABLE_STAT2
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else if( nEq==0 && pProbe->aSample ){
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pFirstEqTerm = pTerm;
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}
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if( nEq==0 && pProbe->aSample ) pFirstTerm = pTerm;
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#endif
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used |= pTerm->prereqRight;
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}
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@ -2796,8 +2863,12 @@ static void bestBtreeIndex(
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** to get a better estimate on the number of rows based on
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** VALUE and how common that value is according to the histogram.
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*/
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if( nRow>(double)1 && nEq==1 && pFirstEqTerm!=0 ){
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whereEqScanEst(pParse, pProbe, pFirstEqTerm, &nRow);
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if( nRow>(double)1 && nEq==1 && pFirstTerm!=0 ){
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if( pFirstTerm->eOperator==WO_EQ ){
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whereEqualScanEst(pParse, pProbe, pFirstTerm->pExpr->pRight, &nRow);
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}else if( pFirstTerm->eOperator==WO_IN && bInEst==0 ){
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whereInScanEst(pParse, pProbe, pFirstTerm->pExpr->x.pList, &nRow);
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}
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}
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#endif /* SQLITE_ENABLE_STAT2 */
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