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Add a note pointing out that is_pseudo_constant_clause() doesn't check

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for aggregates.  This is OK for current uses but could burn somebody
someday...
This commit is contained in:
Tom Lane 2007-01-17 17:25:52 +00:00
parent eddbf39756
commit c81bfc244b
1 changed files with 7 additions and 1 deletions
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8
src/backend/optimizer/util/clauses.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.229 2007/01/10 18:06:04 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.230 2007/01/17 17:25:52 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@ -1073,6 +1073,12 @@ is_strict_saop(ScalarArrayOpExpr *expr, bool falseOK)
* may vary from one statement to the next. However, the expr's value
* will be constant over any one scan of the current query, so it can be
* used as, eg, an indexscan key.
*
* CAUTION: this function omits to test for one very important class of
* not-constant expressions, namely aggregates (Aggrefs). In current usage
* this is only applied to WHERE clauses and so a check for Aggrefs would be
* a waste of cycles; but be sure to also check contain_agg_clause() if you
* want to know about pseudo-constness in other contexts.
*/
bool
is_pseudo_constant_clause(Node *clause)