-<!-- $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>
<para>
Currently, <varname>constraint_exclusion</> is disabled by
- default because it risks incorrect results if query plans are
- cached — 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