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Merge trunk enhancements into the right-join branch.

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FossilOrigin-Name: 3fd9706bba4a71cb5c7ce1341c3be0a7727941445820a073e7b2f0f32512e8ef
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drh
2022-04-28 12:52:49 +00:00
parent 7980fadcef 22b541b55a
commit 09121b0523
11 changed files with 108 additions and 42 deletions
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36
src/expr.c
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@@ -2297,6 +2297,42 @@ int sqlite3ExprIsTableConstant(Expr *p, int iCur){
return exprIsConst(p, 3, iCur);
}
/*
** Check pExpr to see if it is an invariant constraint on data source pSrc.
** This is an optimization. False negatives will perhaps cause slower
** queries, but false positives will yield incorrect answers. So when in
** doubt, return 0.
**
** To be an invariant constraint, the following must be true:
**
** (1) pExpr cannot refer to any table other than pSrc->iCursor.
**
** (2) pExpr cannot use subqueries or non-deterministic functions.
**
** (3) pSrc cannot be part of the left operand for a RIGHT JOIN.
** (Is there some way to relax this constraint?)
**
** (4) If pSrc is the right operand of a LEFT JOIN, then...
** (4a) pExpr must come from an ON clause..
(4b) and specifically the ON clause associated with the LEFT JOIN.
**
** (5) If pSrc is not the right operand of a LEFT JOIN or the left
** operand of a RIGHT JOIN, then pExpr must be from the WHERE
** clause, not an ON clause.
*/
int sqlite3ExprIsTableConstraint(Expr *pExpr, const SrcItem *pSrc){
if( pSrc->fg.jointype & JT_LTORJ ){
return 0; /* rule (3) */
}
if( pSrc->fg.jointype & JT_LEFT ){
if( !ExprHasProperty(pExpr, EP_FromJoin) ) return 0; /* rule (4a) */
if( pExpr->w.iJoin!=pSrc->iCursor ) return 0; /* rule (4b) */
}else{
if( ExprHasProperty(pExpr, EP_FromJoin) ) return 0; /* rule (5) */
}
return sqlite3ExprIsTableConstant(pExpr, pSrc->iCursor); /* rules (1), (2) */
}
/*
** sqlite3WalkExpr() callback used by sqlite3ExprIsConstantOrGroupBy().