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Suppress subquery pullup/pushdown when a subquery contains volatile

2006年8月19日 02:48:53 +0000 (02:48 +0000)

functions in its targetlist, to avoid introducing multiple evaluations
of volatile functions that textually appear only once. This is a
slightly tighter version of Jaime Casanova's recent patch.

src/backend/optimizer/path/allpaths.c patch | blob | blame | history

src/backend/optimizer/prep/prepjointree.c patch | blob | blame | history

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c

index fc618f72d1cc0878fafc8bff66a113c718de9391..794c14fbbabc2b05f1e468daa607e87a0d5734b2 100644 (file)

--- a/src/backend/optimizer/path/allpaths.c

+++ b/src/backend/optimizer/path/allpaths.c

@@ -8,7 +8,7 @@

* IDENTIFICATION

- * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.151 2006年08月10日 02:36:28 tgl Exp $

+ * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.152 2006年08月19日 02:48:53 tgl Exp $

*-------------------------------------------------------------------------

@@ -871,6 +871,10 @@ compare_tlist_datatypes(List *tlist, List *colTypes,

* 5. We must not push down any quals that refer to subselect outputs that

* return sets, else we'd introduce functions-returning-sets into the

* subquery's WHERE/HAVING quals.

+ *

+ * 6. We must not push down any quals that refer to subselect outputs that

+ * contain volatile functions, for fear of introducing strange results due

+ * to multiple evaluation of a volatile function.

static bool

qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,

@@ -940,6 +944,13 @@ qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,

safe = false;

break;

}

+ /* Refuse volatile functions (point 6) */

+ if (contain_volatile_functions((Node *) tle->expr))

+ {

+ safe = false;

+ break;

+ }

}

list_free(vars);

diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c

index ef92d9d3c9f33cb54e013f583dfa6d4849f90001..bea7c03a739e3ad01b89a1abb2b5a08d682ea945 100644 (file)

--- a/src/backend/optimizer/prep/prepjointree.c

+++ b/src/backend/optimizer/prep/prepjointree.c

@@ -15,7 +15,7 @@

* IDENTIFICATION

- * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.42 2006年08月12日 20:05:55 tgl Exp $

+ * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.43 2006年08月19日 02:48:53 tgl Exp $

*-------------------------------------------------------------------------

@@ -656,6 +656,15 @@ is_simple_subquery(Query *subquery)

if (expression_returns_set((Node *) subquery->targetList))

return false;

+ /*

+ * Don't pull up a subquery that has any volatile functions in its

+ * targetlist. Otherwise we might introduce multiple evaluations of

+ * these functions, if they get copied to multiple places in the upper

+ * query, leading to surprising results.

+ */

+ if (contain_volatile_functions((Node *) subquery->targetList))

+ return false;

* Hack: don't try to pull up a subquery with an empty jointree.

* query_planner() will correctly generate a Result plan for a jointree

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