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Remove assertion that constraint_exclusion risks wrong answers if 

table constraints are changed; this is no longer true now that we
have a plan invalidation mechanism.
This commit is contained in:
Tom Lane 2007-03-26 01:41:57 +00:00
parent dc1b8cea93
commit 287ed68dd2
1 changed files with 2 additions and 8 deletions
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10
doc/src/sgml/config.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.117 2007/03/22 15:46:56 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.118 2007/03/26 01:41:57 tgl Exp $ -->
<chapter Id="runtime-config">
<title>Server Configuration</title>
@ -2140,13 +2140,7 @@ SELECT * FROM parent WHERE key = 2400;
<para>
Currently, <varname>constraint_exclusion</> is disabled by
default because it risks incorrect results if query plans are
cached &mdash; if a table constraint is changed or dropped,
the previously generated plan might now be wrong, and there is
no built-in mechanism to force re-planning. (This deficiency
will probably be addressed in a future
<productname>PostgreSQL</> release.) Another reason for
keeping it off is that the constraint checks are relatively
default because the constraint checks are relatively
expensive, and in many circumstances will yield no savings.
It is recommended to turn this on only if you are actually
using partitioned tables designed to take advantage of the