Fire non-deferred AFTER triggers immediately upon query completion,

rather than when returning to the idle loop.  This makes no particular
difference for interactively-issued queries, but it makes a big difference
for queries issued within functions: trigger execution now occurs before
the calling function is allowed to proceed.  This responds to numerous
complaints about nonintuitive behavior of foreign key checking, such as
http://archives.postgresql.org/pgsql-bugs/2004-09/msg00020.php, and
appears to be required by the SQL99 spec.
Also take the opportunity to simplify the data structures used for the
pending-trigger list, rename them for more clarity, and squeeze out a
bit of space.

2 files changed, 39 insertions, 18 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>
 
diff --git a/doc/src/sgml/release.sgml b/doc/src/sgml/release.sgml
index b742f675e30..ddf93a04ff9 100644
--- a/doc/src/sgml/release.sgml
+++ b/doc/src/sgml/release.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.294 2004/08/30 00:47:31 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.295 2004/09/10 18:39:54 tgl Exp $
 -->
 
 <appendix id="release">
@@ -336,6 +336,16 @@ $PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.294 2004/08/30 00:47:31 tgl Exp
        whitespace (which has always been ignored).
       </para>
      </listitem>
+
+     <listitem>
+      <para>
+       Non-deferred AFTER triggers are now fired immediately after completion
+       of the triggering query, rather than upon finishing the current
+       interactive command.  This makes a difference when the triggering query
+       occurred within a function: the trigger is invoked before the function
+       proceeds to its next operation.
+      </para>
+     </listitem>
     </itemizedlist>
    </para>
   </sect2>
@@ -1426,6 +1436,18 @@ $PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.294 2004/08/30 00:47:31 tgl Exp
 
     <listitem>
      <para>
+      Non-deferred AFTER triggers are now fired immediately after completion
+      of the triggering query, rather than upon finishing the current
+      interactive command.  This makes a difference when the triggering query
+      occurred within a function: the trigger is invoked before the function
+      proceeds to its next operation.  For example, if a function inserts
+      a new row into a table, any non-deferred foreign key checks occur
+      before proceeding with the function.
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
       Allow function parameters to be declared with names (Dennis Bjorklund)
      </para>
      <para>
@@ -1483,7 +1505,7 @@ $PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.294 2004/08/30 00:47:31 tgl Exp
 
     <listitem>
      <para>
-      New plperl server-side language (Command Prompt, Andrew Dunstan)
+      Major overhaul of plperl server-side language (Command Prompt, Andrew Dunstan)
      </para>
     </listitem>