-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_constraints.sgml,v 1.17 2009/07/29 20:56:17 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_constraints.sgml,v 1.18 2010/01/18 00:32:21 tgl Exp $ -->
<refentry id="SQL-SET-CONSTRAINTS">
<refmeta>
<refentrytitle id="SQL-SET-CONSTRAINTS-title">SET CONSTRAINTS</refentrytitle>
<refnamediv>
<refname>SET CONSTRAINTS</refname>
- <refpurpose>set constraint checking modes for the current transaction</refpurpose>
+ <refpurpose>set constraint check timing for the current transaction</refpurpose>
</refnamediv>
<indexterm zone="sql-set-constraints">
<para>
<command>SET CONSTRAINTS</command> with a list of constraint names changes
- the mode of just those constraints (which must all be deferrable). The
+ the mode of just those constraints (which must all be deferrable). Each
+ constraint name can be schema-qualified. The
current schema search path is used to find the first matching name if
no schema name is specified. <command>SET CONSTRAINTS ALL</command>
changes the mode of all deferrable constraints.
</para>
<para>
- Currently, only <literal>UNIQUE</>, <literal>PRIMARY KEY</>, and
- <literal>REFERENCES</> (foreign key) constraints are affected by this
- setting. <literal>NOT NULL</> and <literal>CHECK</> constraints are
+ Currently, only <literal>UNIQUE</>, <literal>PRIMARY KEY</>,
+ <literal>REFERENCES</> (foreign key), and <literal>EXCLUDE</>
+ constraints are affected by this setting.
+ <literal>NOT NULL</> and <literal>CHECK</> constraints are
always checked immediately when a row is inserted or modified
(<emphasis>not</> at the end of the statement).
- Uniqueness constraints that have not been declared <literal>DEFERRABLE</>
- are also checked immediately.
+ Uniqueness and exclusion constraints that have not been declared
+ <literal>DEFERRABLE</> are also checked immediately.
</para>
<para>
<refsect1>
<title>Notes</title>
+ <para>
+ Because <productname>PostgreSQL</productname> does not require constraint
+ names to be unique within a schema (but only per-table), it is possible
+ that there is more than one match for a specified constraint name.
+ In this case <command>SET CONSTRAINTS</command> will act on all matches.
+ For a non-schema-qualified name, once a match or matches have been found in
+ some schema in the search path, schemas appearing later in the path are not
+ searched.
+ </para>
+
<para>
This command only alters the behavior of constraints within the
current transaction. Thus, if you execute this command outside of a
<para>
This command complies with the behavior defined in the SQL
standard, except for the limitation that, in
- <productname>PostgreSQL</productname>, it only applies to
- foreign-key and uniqueness constraints.
+ <productname>PostgreSQL</productname>, it does not apply to
+ <literal>NOT NULL</> and <literal>CHECK</> constraints.
+ Also, <productname>PostgreSQL</productname> checks non-deferrable
+ uniqueness constraints immediately, not at end of statement as the
+ standard would suggest.
</para>
</refsect1>