Add a new system view, pg_prepared_statements, that can be used to

access information about the prepared statements that are available
in the current session. Original patch from Joachim Wieland, various
improvements by Neil Conway.

The "statement" column of the view contains the literal query string
sent by the client, without any rewriting or pretty printing. This
means that prepared statements created via SQL will be prefixed with
"PREPARE ... AS ", whereas those prepared via the FE/BE protocol will
not. That is unfortunate, but discussion on -patches did not yield an
efficient way to improve this, and there is some merit in returning
exactly what the client sent to the backend.

Catalog version bumped, regression tests updated.

doc/src/sgml/catalogs.sgml

@@ -1,6 +1,6 @@
 <!--
  Documentation of the system catalogs, directed toward PostgreSQL developers
- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.115 2005/11/04 23:13:59 petere Exp $
+ $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.116 2006/01/08 07:00:24 neilc Exp $
  -->
 
 <chapter id="catalogs">
@@ -4372,6 +4372,11 @@
       <entry>currently held locks</entry>
      </row>
 
+     <row>
+      <entry><link linkend="view-pg-prepared-statements"><structname>pg_prepared_statements</structname></link></entry>
+      <entry>current prepared statements</entry>
+     </row>
+
      <row>
       <entry><link linkend="view-pg-prepared-xacts"><structname>pg_prepared_xacts</structname></link></entry>
       <entry>currently prepared transactions</entry>
@@ -4778,6 +4783,101 @@
 
  </sect1>
 
+ <sect1 id="view-pg-prepared-statements">
+  <title><structname>pg_prepared_statements</structname></title>
+
+  <indexterm zone="view-pg-prepared-statements">
+   <primary>pg_prepared_statements</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_prepared_statements</structname> view displays
+   all the prepared statements that are available in the current
+   session. See <xref linkend="sql-prepare"
+   endterm="sql-prepare-title"> for more information about prepared
+   statements.
+  </para>
+
+  <para>
+   <structname>pg_prepared_statements</structname> contains one row
+   for each prepared statement. Rows are added to the view when a new
+   prepared statement is created, and removed when a prepared
+   statement is released (for example, via the <xref
+   linkend="sql-deallocate" endterm="sql-deallocate-title">
+   command).
+  </para>
+
+  <table>
+   <title><structname>pg_prepared_statements</> Columns</title>
+
+   <tgroup cols=4>
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>References</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+    <tbody>
+     <row>
+      <entry><structfield>name</structfield></entry>
+      <entry><type>text</type></entry>
+      <entry></entry>
+      <entry>
+       The identifier of the prepared statement.
+      </entry>
+     </row>
+     <row>
+      <entry><structfield>statement</structfield></entry>
+      <entry><type>text</type></entry>
+      <entry></entry>
+      <entry>
+       The query string submitted by the client to create this
+       prepared statement. For prepared statements created via SQL,
+       this is the <command>PREPARE</command> statement submitted by
+       the client. For prepared statements created via the
+       frontend/backend protocol, this is the text of the prepared
+       statement itself.
+      </entry>
+     </row>
+     <row>
+      <entry><structfield>prepare_time</structfield></entry>
+      <entry><type>timestamptz</type></entry>
+      <entry></entry>
+      <entry>
+       The time at which the prepared statement was created.
+      </entry>
+     </row>
+     <row>
+      <entry><structfield>parameter_types</structfield></entry>
+      <entry><type>oid[]</type></entry>
+      <entry></entry>
+      <entry>
+       The expected parameter types for the prepared statement in the form of
+       an array of type OIDs.
+      </entry>
+     </row>
+     <row>
+      <entry><structfield>from_sql</structfield></entry>
+      <entry><type>boolean</type></entry>
+      <entry></entry>
+      <entry>
+       <literal>true</literal> if the prepared statement was created
+       via the <command>PREPARE</command> SQL statement;
+       <literal>false</literal> if the statement was prepared via the
+       frontend/backend protocol.
+      </entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <para>
+   The <structname>pg_prepared_statements</structname> view is read only.
+  </para>
+ </sect1>
+
  <sect1 id="view-pg-prepared-xacts">
   <title><structname>pg_prepared_xacts</structname></title>
 

doc/src/sgml/ref/prepare.sgml

@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/prepare.sgml,v 1.16 2005/10/15 01:47:12 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/prepare.sgml,v 1.17 2006/01/08 07:00:25 neilc Exp $
 PostgreSQL documentation
 -->
 
@@ -145,6 +145,11 @@ PREPARE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable c
    the <xref linkend="sql-analyze" endterm="sql-analyze-title">
    documentation.
   </para>
+
+  <para>
+   You can see all available prepared statements of a session by querying the
+   <structname>pg_prepared_statements</> system view.
+  </para>
  </refsect1>
 
  <refsect1 id="sql-prepare-examples">