From: drh Date: Wed, 27 Jul 2016 18:27:02 +0000 (+0000) Subject: When estimating the cost of an index scan, factor in the cost savings of X-Git-Tag: version-3.14.0~34^2~1 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2409f8a11232ff4e2999168f01e954502f189f02;p=thirdparty%2Fsqlite.git When estimating the cost of an index scan, factor in the cost savings of being able to use the index to evaluate some WHERE clause terms without having to do a table lookup. FossilOrigin-Name: a59b5622f7cc6e502d71aabc12c053582cd03609 --- diff --git a/manifest b/manifest index 7f897eb954..0e15122481 100644 --- a/manifest +++ b/manifest @@ -1,5 +1,5 @@ -C Ensure\sthat\sthe\ssqlite3_scrub_backup()\sextension\screates\sa\sbackup\sdatabase\sat\sleast\sas\slarge\sas\sindicated\sby\sthe\sdatabase\sheader,\seven\sif\sthe\slast\spage\sof\sthe\sinput\sdatabase\sis\sa\sfree-list\sleaf. -D 2016-07-26T10:46:21.988 +C When\sestimating\sthe\scost\sof\san\sindex\sscan,\sfactor\sin\sthe\scost\ssavings\sof\nbeing\sable\sto\suse\sthe\sindex\sto\sevaluate\ssome\sWHERE\sclause\sterms\swithout\nhaving\sto\sdo\sa\stable\slookup. +D 2016-07-27T18:27:02.556 F Makefile.in 6c20d44f72d4564f11652b26291a214c8367e5db F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434 F Makefile.msc d66d0395c38571aab3804f8db0fa20707ae4609a @@ -337,7 +337,7 @@ F src/ctime.c 61949e83c4c36e37195a8398ebc752780b534d95 F src/date.c 1cc9fb516ec9932c6fd4d2a0d2f8bc4480145c39 F src/dbstat.c 4f6f7f52b49beb9636ffbd517cfe44a402ba4ad0 F src/delete.c 4aba4214a377ce8ddde2d2e609777bcc8235200f -F src/expr.c 21b153e1046c624e9387a17d3261f69b461e700c +F src/expr.c 3347e66d4e27ec5f3ec7573b9a5f899bbd7d1df8 F src/fault.c 160a0c015b6c2629d3899ed2daf63d75754a32bb F src/fkey.c bc4145347595b7770f9a598cff1c848302cf5413 F src/func.c 61a4114cf7004f10c542cfabbab9f2bcb9033045 @@ -388,7 +388,7 @@ F src/shell.c 9351fc6de11e1d908648c0a92d85627138e3dee5 F src/sqlite.h.in c6e68a4a47610631822a4f8f83a44c9f75339331 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8 F src/sqlite3ext.h 46f300b6e300e0fa916d7d58c44b53415b8471a9 -F src/sqliteInt.h 49081ceab08eda9943d555aee57392c5b35d1c60 +F src/sqliteInt.h d25c18c1272a7811e2569c39bfc2fca96156eead F src/sqliteLimit.h c0373387c287c8d0932510b5547ecde31b5da247 F src/status.c 5b18f9526900f61189ab0b83f1ef41d9f871a2ab F src/table.c 5226df15ab9179b9ed558d89575ea0ce37b03fc9 @@ -463,7 +463,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9 F src/wal.c 02eeecc265f6ffd0597378f5d8ae9070b62a406a F src/wal.h 6dd221ed384afdc204bc61e25c23ef7fd5a511f2 F src/walker.c 0f142b5bd3ed2041fc52d773880748b212e63354 -F src/where.c 48eed8ebe319c6cbc7bf7682018f32af0f5189f5 +F src/where.c 7e4d676b5ac4434e5f93606a744d396dc40d9977 F src/whereInt.h e5b939701a7ceffc5a3a8188a37f9746416ebcd0 F src/wherecode.c 99707d11907c71d289ee9553d2d1a22f1fd8ba41 F src/whereexpr.c d7dcbf14ce1b5876c1f76496162c30fcba669563 @@ -1507,7 +1507,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0 -P c0e7d98ef2a13ede5ae865083ede1aaffdf43310 -R 783c6677056c1c6297ef166e24fadbce -U dan -Z 42a389186c57610d077ea553714cade1 +P 483994a54dee3c7a3801e0e9d3c96fa9dbd8d2fd +R 9e4bd013f5c2cf2171d472668aed0d1c +T *branch * improved-index-scan +T *sym-improved-index-scan * +T -sym-trunk * +U drh +Z 8f3398744130761f466da0e8b7212fe4 diff --git a/manifest.uuid b/manifest.uuid index 1e810448d2..6da37e4d78 100644 --- a/manifest.uuid +++ b/manifest.uuid @@ -1 +1 @@ -483994a54dee3c7a3801e0e9d3c96fa9dbd8d2fd \ No newline at end of file +a59b5622f7cc6e502d71aabc12c053582cd03609 \ No newline at end of file diff --git a/src/expr.c b/src/expr.c index ea52d66253..c027cf02a4 100644 --- a/src/expr.c +++ b/src/expr.c @@ -3965,6 +3965,61 @@ int sqlite3ExprImpliesExpr(Expr *pE1, Expr *pE2, int iTab){ return 0; } +/* +** An instance of the following structure is used by the tree walker +** to determine if an expression can be evaluated by reference to the +** index only, without having to do a search for the corresponding +** table entry. The IdxCover.pIdx field is the index. IdxCover.iCur +** is the cursor for the table. +*/ +struct IdxCover { + Index *pIdx; /* The index to be tested for coverage */ + int iCur; /* Cursor number for the table corresponding to the index */ +}; + +/* +** Check to see if there are references to columns in table +** pWalker->u.pIdxCover->iCur can be satisfied using the index +** pWalker->u.pIdxCover->pIdx. +*/ +static int exprIdxCover(Walker *pWalker, Expr *pExpr){ + if( pExpr->op==TK_COLUMN + && pExpr->iTable==pWalker->u.pIdxCover->iCur + && sqlite3ColumnOfIndex(pWalker->u.pIdxCover->pIdx, pExpr->iColumn)<0 + ){ + pWalker->eCode = 1; + return WRC_Abort; + } + return WRC_Continue; +} + +/* +** Determine if an index on table iCur that contains the columns in +** Bitmask m will cover the expression pExpr. Return true if the index +** does cover the expression and false if the expression references +** table columns that are not found in the index. +** +** An index covering an expression means that the expression can be +** evaluated using only the index and without having to lookup the +** corresponding table entry. +*/ +int sqlite3ExprCoveredByIndex( + Expr *pExpr, /* The index to be tested */ + int iCur, /* The cursor number for the corresponding table */ + Index *pIdx /* The index that might be used for coverage */ +){ + Walker w; + struct IdxCover xcov; + memset(&w, 0, sizeof(w)); + xcov.iCur = iCur; + xcov.pIdx = pIdx; + w.xExprCallback = exprIdxCover; + w.u.pIdxCover = &xcov; + sqlite3WalkExpr(&w, pExpr); + return !w.eCode; +} + + /* ** An instance of the following structure is used by the tree walker ** to count references to table columns in the arguments of an diff --git a/src/sqliteInt.h b/src/sqliteInt.h index 879e6703ca..c5b1eccc03 100644 --- a/src/sqliteInt.h +++ b/src/sqliteInt.h @@ -3257,6 +3257,7 @@ struct Walker { struct SrcCount *pSrcCount; /* Counting column references */ struct CCurHint *pCCurHint; /* Used by codeCursorHint() */ int *aiCol; /* array of column indexes */ + struct IdxCover *pIdxCover; /* Check for index coverage */ } u; }; @@ -3700,6 +3701,7 @@ int sqlite3ExprListCompare(ExprList*, ExprList*, int); int sqlite3ExprImpliesExpr(Expr*, Expr*, int); void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*); void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*); +int sqlite3ExprCoveredByIndex(Expr*, int iCur, Index *pIdx); int sqlite3FunctionUsesThisSrc(Expr*, SrcList*); Vdbe *sqlite3GetVdbe(Parse*); #ifndef SQLITE_OMIT_BUILTIN_TEST diff --git a/src/where.c b/src/where.c index a65f30968e..6a02574921 100644 --- a/src/where.c +++ b/src/where.c @@ -2775,11 +2775,34 @@ static int whereLoopAddBtree( /* The cost of visiting the index rows is N*K, where K is ** between 1.1 and 3.0, depending on the relative sizes of the - ** index and table rows. If this is a non-covering index scan, - ** also add the cost of visiting table rows (N*3.0). */ + ** index and table rows. */ pNew->rRun = rSize + 1 + (15*pProbe->szIdxRow)/pTab->szTabRow; if( m!=0 ){ - pNew->rRun = sqlite3LogEstAdd(pNew->rRun, rSize+16); + /* If this is a non-covering index scan, add in the cost of + ** doing table lookups. The cost will be 3x the number of + ** lookups. Take into account WHERE clause terms that can be + ** satisfied using just the index, and that do not require a + ** table lookup. */ + LogEst nLookup = rSize + 16; /* Base cost: N*3 */ + int ii; + int iCur = pSrc->iCursor; + WhereClause *pWC = &pWInfo->sWC; + for(ii=0; iinTerm; ii++){ + WhereTerm *pTerm = &pWC->a[ii]; + if( !sqlite3ExprCoveredByIndex(pTerm->pExpr, iCur, pProbe) ){ + break; + } + /* pTerm can be evaluated using just the index. So reduce + ** the expected number of table lookups accordingly */ + if( pTerm->truthProb<=0 ){ + nLookup += pTerm->truthProb; + }else{ + nLookup--; + if( pTerm->eOperator & (WO_EQ|WO_IS) ) nLookup -= 19; + } + } + + pNew->rRun = sqlite3LogEstAdd(pNew->rRun, nLookup); } ApplyCostMultiplier(pNew->rRun, pTab->costMult); whereLoopOutputAdjust(pWC, pNew, rSize);