diff options
Diffstat (limited to 'doc/src/sgml/ref/set_constraints.sgml')
| -rw-r--r-- | doc/src/sgml/ref/set_constraints.sgml | 31 |
1 files changed, 15 insertions, 16 deletions
diff --git a/doc/src/sgml/ref/set_constraints.sgml b/doc/src/sgml/ref/set_constraints.sgml index 0c976c93e25..3bcde91f386 100644 --- a/doc/src/sgml/ref/set_constraints.sgml +++ b/doc/src/sgml/ref/set_constraints.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_constraints.sgml,v 1.11 2004/09/08 20:47:37 tgl Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_constraints.sgml,v 1.12 2004/09/10 18:39:53 tgl Exp $ --> <refentry id="SQL-SET-CONSTRAINTS"> <refmeta> <refentrytitle id="SQL-SET-CONSTRAINTS-title">SET CONSTRAINTS</refentrytitle> @@ -34,13 +34,13 @@ SET CONSTRAINTS { ALL | <replaceable class="parameter">name</replaceable> [, ... <para> Upon creation, a constraint is given one of three - characteristics: <literal>INITIALLY DEFERRED</literal>, - <literal>INITIALLY IMMEDIATE DEFERRABLE</literal>, or - <literal>INITIALLY IMMEDIATE NOT DEFERRABLE</literal>. The third - class is not affected by the <command>SET CONSTRAINTS</command> - command. The first two classes start every transaction in the - indicated mode, but their behavior can be changed within a transaction - by <command>SET CONSTRAINTS</command>. + characteristics: <literal>DEFERRABLE INITIALLY DEFERRED</literal>, + <literal>DEFERRABLE INITIALLY IMMEDIATE</literal>, or + <literal>NOT DEFERRABLE</literal>. The third + class is always <literal>IMMEDIATE</literal> and is not affected by the + <command>SET CONSTRAINTS</command> command. The first two classes start + every transaction in the indicated mode, but their behavior can be changed + within a transaction by <command>SET CONSTRAINTS</command>. </para> <para> @@ -52,19 +52,22 @@ SET CONSTRAINTS { ALL | <replaceable class="parameter">name</replaceable> [, ... </para> <para> - When you change the mode of a constraint from <literal>DEFERRED</literal> + When <command>SET CONSTRAINTS</command> changes the mode of a constraint + from <literal>DEFERRED</literal> to <literal>IMMEDIATE</literal>, the new mode takes effect retroactively: any outstanding data modifications that would have been checked at the end of the transaction are instead checked during the execution of the <command>SET CONSTRAINTS</command> command. If any such constraint is violated, the <command>SET CONSTRAINTS</command> - fails (and does not change the constraint mode). + fails (and does not change the constraint mode). Thus, <command>SET + CONSTRAINTS</command> can be used to force checking of constraints to + occur at a specific point in a transaction. </para> <para> Currently, only foreign key constraints are affected by this setting. Check and unique constraints are always effectively - initially immediate not deferrable. + not deferrable. </para> </refsect1> @@ -76,11 +79,7 @@ SET CONSTRAINTS { ALL | <replaceable class="parameter">name</replaceable> [, ... current transaction. Thus, if you execute this command outside of a transaction block (<command>BEGIN</command>/<command>COMMIT</command> pair), it will - not appear to have any effect. If you wish to change the behavior - of a constraint without needing to issue a <command>SET - CONSTRAINTS</command> command in every transaction, specify - <literal>INITIALLY DEFERRED</literal> or <literal>INITIALLY - IMMEDIATE</literal> when you create the constraint. + not appear to have any effect. </para> </refsect1> |