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Overview
Comment: | When testing non-indexed WHERE constraints, test those that involve correlated sub-queries last of all. This increases the chances of not having to run the sub-query at all. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | defer-where-subqueries |
Files: | files | file ages | folders |
SHA3-256: |
1f9c1f359e4693954ba7e2bc7b172ef3 |
User & Date: | dan 2017-07-10 14:33:00.503 |
Context
2017-07-10
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14:39 | Fix a problem causing non-covered WHERE terms to be evaluated before covered WHERE terms. (check-in: 7d3cb39f60 user: dan tags: defer-where-subqueries) | |
14:33 | When testing non-indexed WHERE constraints, test those that involve correlated sub-queries last of all. This increases the chances of not having to run the sub-query at all. (check-in: 1f9c1f359e user: dan tags: defer-where-subqueries) | |
13:24 | For sqlite3TreeView() debugging output, show the Expr.flags field on scalar subqueries. (check-in: dc857a96b0 user: drh tags: trunk) | |
Changes
Changes to src/sqliteInt.h.
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2394 2395 2396 2397 2398 2399 2400 | #define EP_Subquery 0x200000 /* Tree contains a TK_SELECT operator */ #define EP_Alias 0x400000 /* Is an alias for a result set column */ #define EP_Leaf 0x800000 /* Expr.pLeft, .pRight, .u.pSelect all NULL */ /* ** Combinations of two or more EP_* flags */ | | | 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 | #define EP_Subquery 0x200000 /* Tree contains a TK_SELECT operator */ #define EP_Alias 0x400000 /* Is an alias for a result set column */ #define EP_Leaf 0x800000 /* Expr.pLeft, .pRight, .u.pSelect all NULL */ /* ** Combinations of two or more EP_* flags */ #define EP_Propagate (EP_Collate|EP_Subquery|EP_VarSelect) /* Prop. up tree */ /* ** These macros can be used to test, set, or clear bits in the ** Expr.flags field. */ #define ExprHasProperty(E,P) (((E)->flags&(P))!=0) #define ExprHasAllProperty(E,P) (((E)->flags&(P))==(P)) |
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Changes to src/wherecode.c.
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1126 1127 1128 1129 1130 1131 1132 | struct SrcList_item *pTabItem; /* FROM clause term being coded */ int addrBrk; /* Jump here to break out of the loop */ int addrHalt; /* addrBrk for the outermost loop */ int addrCont; /* Jump here to continue with next cycle */ int iRowidReg = 0; /* Rowid is stored in this register, if not zero */ int iReleaseReg = 0; /* Temp register to free before returning */ Index *pIdx = 0; /* Index used by loop (if any) */ | | | 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 | struct SrcList_item *pTabItem; /* FROM clause term being coded */ int addrBrk; /* Jump here to break out of the loop */ int addrHalt; /* addrBrk for the outermost loop */ int addrCont; /* Jump here to continue with next cycle */ int iRowidReg = 0; /* Rowid is stored in this register, if not zero */ int iReleaseReg = 0; /* Temp register to free before returning */ Index *pIdx = 0; /* Index used by loop (if any) */ int iLoop; /* Iteration of constraint generator loop */ pParse = pWInfo->pParse; v = pParse->pVdbe; pWC = &pWInfo->sWC; db = pParse->db; pLevel = &pWInfo->a[iLevel]; pLoop = pLevel->pWLoop; |
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2021 2022 2023 2024 2025 2026 2027 | #ifdef SQLITE_ENABLE_STMT_SCANSTATUS pLevel->addrVisit = sqlite3VdbeCurrentAddr(v); #endif /* Insert code to test every subexpression that can be completely ** computed using the current set of tables. ** | | > > > > > > | < | > > | > | | > > > > > | | | 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 | #ifdef SQLITE_ENABLE_STMT_SCANSTATUS pLevel->addrVisit = sqlite3VdbeCurrentAddr(v); #endif /* Insert code to test every subexpression that can be completely ** computed using the current set of tables. ** ** This loop may run between one and three times, depending on the ** constraints to be generated. The value of stack variable iLoop ** determines the constraints coded by each iteration, as follows: ** ** iLoop==1: Code only expressions that are entirely covered by pIdx. ** iLoop==2: Code remaining expressions that do not contain correlated ** sub-queries. ** iLoop==3: Code all remaining expressions. ** ** An effort is made to skip unnecessary iterations of the loop. */ iLoop = (pIdx ? 1 : 2); do{ int iNext = 0; /* Next value for iLoop */ for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){ Expr *pE; int skipLikeAddr = 0; testcase( pTerm->wtFlags & TERM_VIRTUAL ); testcase( pTerm->wtFlags & TERM_CODED ); if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue; if( (pTerm->prereqAll & pLevel->notReady)!=0 ){ testcase( pWInfo->untestedTerms==0 && (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)!=0 ); pWInfo->untestedTerms = 1; continue; } pE = pTerm->pExpr; assert( pE!=0 ); if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){ continue; } if( iNext==1 && !sqlite3ExprCoveredByIndex(pE, pLevel->iTabCur, pIdx) ){ iNext = 2; continue; } if( iLoop<3 && (pE->flags & EP_VarSelect) ){ if( iNext==0 ) iNext = 3; continue; } if( pTerm->wtFlags & TERM_LIKECOND ){ /* If the TERM_LIKECOND flag is set, that means that the range search ** is sufficient to guarantee that the LIKE operator is true, so we ** can skip the call to the like(A,B) function. But this only works ** for strings. So do not skip the call to the function on the pass ** that compares BLOBs. */ #ifdef SQLITE_LIKE_DOESNT_MATCH_BLOBS continue; #else u32 x = pLevel->iLikeRepCntr; assert( x>0 ); skipLikeAddr = sqlite3VdbeAddOp1(v, (x&1)?OP_IfNot:OP_If, (int)(x>>1)); VdbeCoverage(v); #endif } sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL); if( skipLikeAddr ) sqlite3VdbeJumpHere(v, skipLikeAddr); pTerm->wtFlags |= TERM_CODED; } iLoop = iNext; }while( iLoop>0 ); /* Insert code to test for implied constraints based on transitivity ** of the "==" operator. ** ** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123" ** and we are coding the t1 loop and the t2 loop has not yet coded, ** then we cannot use the "t1.a=t2.b" constraint, but we can code |
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