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authorTom Lane <tgl@sss.pgh.pa.us>2006-12-28 20:02:38 +0000
committerTom Lane <tgl@sss.pgh.pa.us>2006-12-28 20:02:38 +0000
commite1b8a55ec8cc9d77581ad144122f7f7163d82282 (patch)
tree7f22125e389a68fe3ca0b01a4a7105f6a26f4b81
parentc99ddfc43de7d69d903d150a8d372b020371d49a (diff)
downloadpostgresql-e1b8a55ec8cc9d77581ad144122f7f7163d82282.tar.gz
postgresql-e1b8a55ec8cc9d77581ad144122f7f7163d82282.zip
Remove caveat about avoiding cross-type operators in constraints intended
for use with constraint exclusion. We can prove those cases now...
-rw-r--r--doc/src/sgml/ddl.sgml25
1 files changed, 1 insertions, 24 deletions
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index dee6bc70340..6dd740fbfee 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.69 2006/11/28 01:09:01 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.70 2006/12/28 20:02:38 tgl Exp $ -->
<chapter id="ddl">
<title>Data Definition</title>
@@ -2786,29 +2786,6 @@ EXPLAIN SELECT count(*) FROM measurement WHERE logdate &gt;= DATE '2006-01-01';
<listitem>
<para>
- Avoid cross-data type comparisons in the <literal>CHECK</>
- constraints, as the planner will currently fail to prove such
- conditions false. For example, the following constraint
- will work if <varname>x</varname> is an <type>integer</type>
- column, but not if <varname>x</varname> is a
- <type>bigint</type>:
-<programlisting>
-CHECK ( x = 1 )
-</programlisting>
- For a <type>bigint</type> column we must use a constraint like:
-<programlisting>
-CHECK ( x = 1::bigint )
-</programlisting>
- The problem is not limited to the <type>bigint</type> data type
- &mdash; it can occur whenever the default data type of the
- constant does not match the data type of the column to which it
- is being compared. Cross-data type comparisons in the supplied
- queries are usually OK, just not in the <literal>CHECK</> conditions.
- </para>
- </listitem>
-
- <listitem>
- <para>
All constraints on all partitions of the master table are considered for
constraint exclusion, so large numbers of partitions are likely to
increase query planning time considerably.