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Overview
Comment: | Enhance the like optimization so that it works with an ESCAPE clause. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | branch-3.8.9 |
Files: | files | file ages | folders |
SHA3-256: |
2495acf71017fa2ffada18824590ead5 |
User & Date: | drh 2017-07-27 22:16:26.706 |
Context
2017-11-09
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04:13 | Disallow ORDER BY and LIMIT on UPDATE and DELETE of views and WITHOUT ROWID tables. This is a temporary fix for ticket [d4beea1633f1b88f] until a better solution can be found. (check-in: 30aa941fc1 user: drh tags: branch-3.8.9) | |
2017-07-27
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22:16 | Enhance the like optimization so that it works with an ESCAPE clause. (check-in: 2495acf710 user: drh tags: branch-3.8.9) | |
20:24 | Enhance the like optimization so that it works with an ESCAPE clause. (check-in: f5d330f495 user: drh tags: trunk) | |
2017-07-17
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19:37 | Try to push relevant WHERE clause terms of the outer query down into the subquery in order to help the subquery run faster and/or use less memory. This is a cherry-pick of [6df18e949d36] with bug fixes. (check-in: cd6ac07848 user: drh tags: branch-3.8.9) | |
Changes
Changes to src/func.c.
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1645 1646 1647 1648 1649 1650 1651 | setLikeOptFlag(db, "like", caseSensitive ? (SQLITE_FUNC_LIKE | SQLITE_FUNC_CASE) : SQLITE_FUNC_LIKE); } /* ** pExpr points to an expression which implements a function. If ** it is appropriate to apply the LIKE optimization to that function | | | | > > > > > > | < < < > | > > > > > > > > > > | 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 | setLikeOptFlag(db, "like", caseSensitive ? (SQLITE_FUNC_LIKE | SQLITE_FUNC_CASE) : SQLITE_FUNC_LIKE); } /* ** pExpr points to an expression which implements a function. If ** it is appropriate to apply the LIKE optimization to that function ** then set aWc[0] through aWc[2] to the wildcard characters and the ** escape character and then return TRUE. If the function is not a ** LIKE-style function then return FALSE. ** ** The expression "a LIKE b ESCAPE c" is only considered a valid LIKE ** operator if c is a string literal that is exactly one byte in length. ** That one byte is stored in aWc[3]. aWc[3] is set to zero if there is ** no ESCAPE clause. ** ** *pIsNocase is set to true if uppercase and lowercase are equivalent for ** the function (default for LIKE). If the function makes the distinction ** between uppercase and lowercase (as does GLOB) then *pIsNocase is set to ** false. */ int sqlite3IsLikeFunction(sqlite3 *db, Expr *pExpr, int *pIsNocase, char *aWc){ FuncDef *pDef; int nExpr; if( pExpr->op!=TK_FUNCTION || !pExpr->x.pList ){ return 0; } assert( !ExprHasProperty(pExpr, EP_xIsSelect) ); nExpr = pExpr->x.pList->nExpr; pDef = sqlite3FindFunction(db, pExpr->u.zToken, sqlite3Strlen30(pExpr->u.zToken), nExpr, SQLITE_UTF8, 0); if( NEVER(pDef==0) || (pDef->funcFlags & SQLITE_FUNC_LIKE)==0 ){ return 0; } if( nExpr<3 ){ aWc[3] = 0; }else{ Expr *pEscape = pExpr->x.pList->a[2].pExpr; char *zEscape; if( pEscape->op!=TK_STRING ) return 0; zEscape = pEscape->u.zToken; if( zEscape[0]==0 || zEscape[1]!=0 ) return 0; aWc[3] = zEscape[0]; } /* The memcpy() statement assumes that the wildcard characters are ** the first three statements in the compareInfo structure. The ** asserts() that follow verify that assumption */ memcpy(aWc, pDef->pUserData, 3); assert( (char*)&likeInfoAlt == (char*)&likeInfoAlt.matchAll ); |
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Changes to src/where.c.
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653 654 655 656 657 658 659 | int *pnoCase /* True if uppercase is equivalent to lowercase */ ){ const char *z = 0; /* String on RHS of LIKE operator */ Expr *pRight, *pLeft; /* Right and left size of LIKE operator */ ExprList *pList; /* List of operands to the LIKE operator */ int c; /* One character in z[] */ int cnt; /* Number of non-wildcard prefix characters */ | | | 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 | int *pnoCase /* True if uppercase is equivalent to lowercase */ ){ const char *z = 0; /* String on RHS of LIKE operator */ Expr *pRight, *pLeft; /* Right and left size of LIKE operator */ ExprList *pList; /* List of operands to the LIKE operator */ int c; /* One character in z[] */ int cnt; /* Number of non-wildcard prefix characters */ char wc[4]; /* Wildcard characters */ sqlite3 *db = pParse->db; /* Database connection */ sqlite3_value *pVal = 0; int op; /* Opcode of pRight */ if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, wc) ){ return 0; } |
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691 692 693 694 695 696 697 698 699 700 | } sqlite3VdbeSetVarmask(pParse->pVdbe, iCol); assert( pRight->op==TK_VARIABLE || pRight->op==TK_REGISTER ); }else if( op==TK_STRING ){ z = pRight->u.zToken; } if( z ){ cnt = 0; while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){ cnt++; | > > > | > > > > > > > > > > > > | > > > > > > > > > > > > | 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 | } sqlite3VdbeSetVarmask(pParse->pVdbe, iCol); assert( pRight->op==TK_VARIABLE || pRight->op==TK_REGISTER ); }else if( op==TK_STRING ){ z = pRight->u.zToken; } if( z ){ /* Count the number of prefix characters prior to the first wildcard */ cnt = 0; while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){ cnt++; if( c==wc[3] && z[cnt]!=0 ){ if( z[cnt++]>0xc0 ) while( (z[cnt]&0xc0)==0x80 ){ cnt++; } } } /* The optimization is possible only if (1) the pattern does not begin ** with a wildcard and if (2) the non-wildcard prefix does not end with ** an (illegal 0xff) character. The second condition is necessary so ** that we can increment the prefix key to find an upper bound for the ** range search. */ if( cnt!=0 && 255!=(u8)z[cnt-1] ){ Expr *pPrefix; /* A "complete" match if the pattern ends with "*" or "%" */ *pisComplete = c==wc[0] && z[cnt+1]==0; /* Get the pattern prefix. Remove all escapes from the prefix. */ pPrefix = sqlite3Expr(db, TK_STRING, z); if( pPrefix ){ int iFrom, iTo; char *zNew = pPrefix->u.zToken; zNew[cnt] = 0; for(iFrom=iTo=0; iFrom<cnt; iFrom++){ if( zNew[iFrom]==wc[3] ) iFrom++; zNew[iTo++] = zNew[iFrom]; } zNew[iTo] = 0; } *ppPrefix = pPrefix; /* If the RHS pattern is a bound parameter, make arrangements to ** reprepare the statement when that parameter is rebound */ if( op==TK_VARIABLE ){ Vdbe *v = pParse->pVdbe; sqlite3VdbeSetVarmask(v, pRight->iColumn); if( *pisComplete && pRight->u.zToken[1] ){ /* If the rhs of the LIKE expression is a variable, and the current ** value of the variable means there is no need to invoke the LIKE ** function, then no OP_Variable will be added to the program. |
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Changes to test/like.test.
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944 945 946 947 948 949 950 951 952 | SELECT id FROM t12nc WHERE x LIKE 'abc%' COLLATE binary ORDER BY +id; } {/SEARCH/} do_execsql_test like-12.16 { EXPLAIN QUERY PLAN SELECT id FROM t12b WHERE x LIKE 'abc%' COLLATE binary ORDER BY +id; } {/SCAN/} finish_test | > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 | SELECT id FROM t12nc WHERE x LIKE 'abc%' COLLATE binary ORDER BY +id; } {/SEARCH/} do_execsql_test like-12.16 { EXPLAIN QUERY PLAN SELECT id FROM t12b WHERE x LIKE 'abc%' COLLATE binary ORDER BY +id; } {/SCAN/} # As of 2017-07-27 (3.21.0) the LIKE optimization works with ESCAPE as # long as the ESCAPE is a single-byte literal. # db close sqlite3 db :memory: do_execsql_test like-15.100 { CREATE TABLE t15(x TEXT COLLATE nocase, y, PRIMARY KEY(x)); INSERT INTO t15(x,y) VALUES ('abcde',1), ('ab%de',2), ('a_cde',3), ('uvwxy',11),('uvwx%',12),('uvwx_',13), ('_bcde',21),('%bcde',22), ('abcd_',31),('abcd%',32), ('ab%xy',41); SELECT y FROM t15 WHERE x LIKE 'ab/%d%' ESCAPE '/'; } {2} do_execsql_test like-15.101 { EXPLAIN QUERY PLAN SELECT y FROM t15 WHERE x LIKE 'ab/%d%' ESCAPE '/'; } {/SEARCH/} do_execsql_test like-15.102 { EXPLAIN QUERY PLAN SELECT y FROM t15 WHERE x LIKE 'ab/%d%' ESCAPE '//'; } {/SCAN/} do_execsql_test like-15.103 { EXPLAIN QUERY PLAN SELECT y FROM t15 WHERE x LIKE 'ab/%d%' ESCAPE ''; } {/SCAN/} do_execsql_test like-15.110 { SELECT y FROM t15 WHERE x LIKE 'abcdx%%' ESCAPE 'x'; } {32} do_execsql_test like-15.111 { SELECT y FROM t15 WHERE x LIKE 'abx%%' ESCAPE 'x' ORDER BY +y } {2 41} do_execsql_test like-15.112 { EXPLAIN QUERY PLAN SELECT y FROM t15 WHERE x LIKE 'abx%%' ESCAPE 'x' ORDER BY +y } {/SEARCH/} do_execsql_test like-15.120 { SELECT y FROM t15 WHERE x LIKE '/%bc%' ESCAPE '/'; } {22} do_execsql_test like-15.121 { EXPLAIN QUERY PLAN SELECT y FROM t15 WHERE x LIKE '/%bc%' ESCAPE '/'; } {/SEARCH/} finish_test |