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Refinements to the determination of when an A==B term is an equivalence.

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Add test cases.

FossilOrigin-Name: 6bfaf525cac2e0c0a4a3bd3a1fc7bf5bd3234303
This commit is contained in:
drh
2015-05-18 11:34:52 +00:00
parent 5820118da5
commit 69c15fee98
4 changed files with 76 additions and 17 deletions
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21
src/where.c
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@@ -1188,17 +1188,18 @@ static void exprAnalyzeOrTerm(
** relation:
** 1. The SQLITE_Transitive optimization must be enabled
** 2. Must be either an == or an IS operator
** 3. Not taken from the ON clause of a LEFT JOIN
** 3. Not originating the ON clause of an OUTER JOIN
** 4. The affinities of A and B must be compatible
** 5. Use the same collating sequence if not numeric affinity
** 5a. Both operands use the same collating sequence OR
** 5b. The overall collating sequence is BINARY
** If this routine returns TRUE, that means that the RHS can be substituted
** for the LHS anyplace else in the WHERE clause where the LHS column occurs.
** This is an optimization. No harm comes from returning 0. But if 1 is
** returned when it should not be, then incorrect answers might result.
*/
static int isEquivalence(Parse *pParse, Expr *pExpr){
static int termIsEquivalence(Parse *pParse, Expr *pExpr){
char aff1, aff2;
CollSeq *pColl1, *pColl2;
CollSeq *pColl;
const char *zColl1, *zColl2;
if( !OptimizationEnabled(pParse->db, SQLITE_Transitive) ) return 0;
if( pExpr->op!=TK_EQ && pExpr->op!=TK_IS ) return 0;
@@ -1210,10 +1211,12 @@ static int isEquivalence(Parse *pParse, Expr *pExpr){
){
return 0;
}
pColl1 = sqlite3ExprCollSeq(pParse, pExpr->pRight);
zColl1 = pColl1 ? pColl1->zName : "BINARY";
pColl2 = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
zColl2 = pColl2 ? pColl2->zName : "BINARY";
pColl = sqlite3BinaryCompareCollSeq(pParse, pExpr->pLeft, pExpr->pRight);
if( pColl==0 || sqlite3StrICmp(pColl->zName, "BINARY")==0 ) return 1;
pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
zColl1 = pColl ? pColl->zName : "BINARY";
pColl = sqlite3ExprCollSeq(pParse, pExpr->pRight);
zColl2 = pColl ? pColl->zName : "BINARY";
return sqlite3StrICmp(zColl1, zColl2)==0;
}
@@ -1315,7 +1318,7 @@ static void exprAnalyze(
pTerm = &pWC->a[idxTerm];
pTerm->wtFlags |= TERM_COPIED;
if( isEquivalence(pParse, pDup) ){
if( termIsEquivalence(pParse, pDup) ){
pTerm->eOperator |= WO_EQUIV;
eExtraOp = WO_EQUIV;
}