diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/where.c | 102 |
1 files changed, 100 insertions, 2 deletions
diff --git a/src/where.c b/src/where.c index 6ecc9c33c..2fe076ba6 100644 --- a/src/where.c +++ b/src/where.c @@ -770,6 +770,79 @@ static void markTermAsChild(WhereClause *pWC, int iChild, int iParent){ pWC->a[iParent].nChild++; } +/* +** Return the N-th AND-connected subterm of pTerm. Or if pTerm is not +** a conjunction, then return just pTerm when N==0. If N is exceeds +** the number of available subterms, return NULL. +*/ +static WhereTerm *whereNthSubterm(WhereTerm *pTerm, int N){ + if( pTerm->eOperator!=WO_AND ){ + return N==0 ? pTerm : 0; + } + if( N<pTerm->u.pAndInfo->wc.nTerm ){ + return &pTerm->u.pAndInfo->wc.a[N]; + } + return 0; +} + +/* +** Subterms pOne and pTwo are contained within WHERE clause pWC. The +** two subterms are in disjunction - they are OR-ed together. +** +** If these two terms are both of the form: "A op B" with the same +** A and B values but different operators and if the operators are +** compatible (if one is = and the other is <, for example) then +** add a new virtual AND term to pWC that is the combination of the +** two. +** +** Some examples: +** +** x<y OR x=y --> x<=y +** x=y OR x=y --> x=y +** x<=y OR x<y --> x<=y +** +** The following is NOT generated: +** +** x<y OR x>y --> x!=y +*/ +static void whereCombineDisjuncts( + SrcList *pSrc, /* the FROM clause */ + WhereClause *pWC, /* The complete WHERE clause */ + WhereTerm *pOne, /* First disjunct */ + WhereTerm *pTwo /* Second disjunct */ +){ + u16 eOp = pOne->eOperator | pTwo->eOperator; + sqlite3 *db; /* Database connection (for malloc) */ + Expr *pNew; /* New virtual expression */ + int op; /* Operator for the combined expression */ + int idxNew; /* Index in pWC of the next virtual term */ + + if( (pOne->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return; + if( (pTwo->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return; + if( (eOp & (WO_EQ|WO_LT|WO_LE))!=eOp + && (eOp & (WO_EQ|WO_GT|WO_GE))!=eOp ) return; + assert( pOne->pExpr->pLeft!=0 && pOne->pExpr->pRight!=0 ); + assert( pTwo->pExpr->pLeft!=0 && pTwo->pExpr->pRight!=0 ); + if( sqlite3ExprCompare(pOne->pExpr->pLeft, pTwo->pExpr->pLeft, -1) ) return; + if( sqlite3ExprCompare(pOne->pExpr->pRight, pTwo->pExpr->pRight, -1) )return; + /* If we reach this point, it means the two subterms can be combined */ + if( (eOp & (eOp-1))!=0 ){ + if( eOp & (WO_LT|WO_LE) ){ + eOp = WO_LE; + }else{ + assert( eOp & (WO_GT|WO_GE) ); + eOp = WO_GE; + } + } + db = pWC->pWInfo->pParse->db; + pNew = sqlite3ExprDup(db, pOne->pExpr, 0); + if( pNew==0 ) return; + for(op=TK_EQ; eOp!=(WO_EQ<<(op-TK_EQ)); op++){ assert( op<TK_GE ); } + pNew->op = op; + idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC); + exprAnalyze(pSrc, pWC, idxNew); +} + #if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY) /* ** Analyze a term that consists of two or more OR-connected @@ -794,6 +867,7 @@ static void markTermAsChild(WhereClause *pWC, int iChild, int iParent){ ** (C) t1.x=t2.y OR (t1.x=t2.z AND t1.y=15) ** (D) x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*') ** (E) (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6) +** (F) x>A OR (x=A AND y>=B) ** ** CASE 1: ** @@ -810,6 +884,16 @@ static void markTermAsChild(WhereClause *pWC, int iChild, int iParent){ ** ** CASE 2: ** +** If there are exactly two disjuncts one side has x>A and the other side +** has x=A (for the same x and A) then add a new virtual conjunct term to the +** WHERE clause of the form "x>=A". Example: +** +** x>A OR (x=A AND y>B) adds: x>=A +** +** The added conjunct can sometimes be helpful in query planning. +** +** CASE 3: +** ** If all subterms are indexable by a single table T, then set ** ** WhereTerm.eOperator = WO_OR @@ -936,12 +1020,26 @@ static void exprAnalyzeOrTerm( } /* - ** Record the set of tables that satisfy case 2. The set might be + ** Record the set of tables that satisfy case 3. The set might be ** empty. */ pOrInfo->indexable = indexable; pTerm->eOperator = indexable==0 ? 0 : WO_OR; + /* For a two-way OR, attempt to implementation case 2. + */ + if( indexable && pOrWc->nTerm==2 ){ + int iOne = 0; + WhereTerm *pOne; + while( (pOne = whereNthSubterm(&pOrWc->a[0],iOne++))!=0 ){ + int iTwo = 0; + WhereTerm *pTwo; + while( (pTwo = whereNthSubterm(&pOrWc->a[1],iTwo++))!=0 ){ + whereCombineDisjuncts(pSrc, pWC, pOne, pTwo); + } + } + } + /* ** chngToIN holds a set of tables that *might* satisfy case 1. But ** we have to do some additional checking to see if case 1 really @@ -1071,7 +1169,7 @@ static void exprAnalyzeOrTerm( }else{ sqlite3ExprListDelete(db, pList); } - pTerm->eOperator = WO_NOOP; /* case 1 trumps case 2 */ + pTerm->eOperator = WO_NOOP; /* case 1 trumps case 3 */ } } } |