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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2006-08-19 02:48:53 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2006-08-19 02:48:53 +0000 |
| commit | fb9e56eea11a970e574260b82d6b05b4fe5a4308 (patch) | |
| tree | 7121fa2a8dc512d9679f4ac3a029f06618f203c5 | |
| parent | 9bf760f7dec703aa34d9bd68aaa982943d24411e (diff) | |
| download | postgresql-fb9e56eea11a970e574260b82d6b05b4fe5a4308.tar.gz postgresql-fb9e56eea11a970e574260b82d6b05b4fe5a4308.zip | |
Suppress subquery pullup/pushdown when a subquery contains volatile
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.
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 13 | ||||
| -rw-r--r-- | src/backend/optimizer/prep/prepjointree.c | 11 |
2 files changed, 22 insertions, 2 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index fc618f72d1c..794c14fbbab 100644 --- 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 2006/08/10 02:36:28 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.152 2006/08/19 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 ef92d9d3c9f..bea7c03a739 100644 --- 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 2006/08/12 20:05:55 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.43 2006/08/19 02:48:53 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -657,6 +657,15 @@ is_simple_subquery(Query *subquery) 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 * that's totally empty, but I don't think the right things happen if an |