diff options
| -rw-r--r-- | src/backend/optimizer/prep/prepjointree.c | 35 |
1 files changed, 16 insertions, 19 deletions
diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c index 687a702c788..05975732133 100644 --- a/src/backend/optimizer/prep/prepjointree.c +++ b/src/backend/optimizer/prep/prepjointree.c @@ -16,7 +16,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.12 2003/09/25 06:58:00 petere Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.13 2003/10/13 23:48:16 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -148,9 +148,10 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join) * If we are inside an outer join, only pull up subqueries whose * targetlists are nullable --- otherwise substituting their tlist * entries for upper Var references would do the wrong thing (the - * results wouldn't become NULL when they're supposed to). XXX - * This could be improved by generating pseudo-variables for such - * expressions; we'd have to figure out how to get the pseudo- + * results wouldn't become NULL when they're supposed to). + * + * XXX This could be improved by generating pseudo-variables for + * such expressions; we'd have to figure out how to get the pseudo- * variables evaluated at the right place in the modified plan * tree. Fix it someday. * @@ -167,7 +168,15 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join) List *rt; /* - * First, pull up any IN clauses within the subquery's WHERE, + * First make a modifiable copy of the subquery. This avoids + * problems if the same subquery is referenced from multiple + * jointree items (which can't happen normally, but might after + * rule rewriting). + */ + subquery = copyObject(subquery); + + /* + * Pull up any IN clauses within the subquery's WHERE, * so that we don't leave unoptimized INs behind. */ if (subquery->hasSubLinks) @@ -175,15 +184,9 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join) subquery->jointree->quals); /* - * Now, recursively pull up the subquery's subqueries, so that + * Recursively pull up the subquery's subqueries, so that * this routine's processing is complete for its jointree and - * rangetable. NB: if the same subquery is referenced from - * multiple jointree items (which can't happen normally, but - * might after rule rewriting), then we will invoke this - * processing multiple times on that subquery. OK because - * nothing will happen after the first time. We do have to be - * careful to copy everything we pull up, however, or risk - * having chunks of structure multiply linked. + * rangetable. * * Note: 'false' is correct here even if we are within an outer * join in the upper query; the lower query starts with a @@ -194,12 +197,6 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join) false); /* - * Now make a modifiable copy of the subquery that we can run - * OffsetVarNodes and IncrementVarSublevelsUp on. - */ - subquery = copyObject(subquery); - - /* * Adjust level-0 varnos in subquery so that we can append its * rangetable to upper query's. */ |