doc: Add note about how to use pg_overexplain.

This commit adds a note to the pg_overexplain page that describes
how to use it (LOAD, session_preload_libraries, or
shared_preload_libraries).  The new text is mostly lifted from the
auto_explain page.  We should probably consider centralizing this
information in the future.

While at it, add a missing "module" to the opening sentence.

Reviewed-by: "David G. Johnston" <[email protected]>
Reviewed-by: Robert Treat <[email protected]>
Reviewed-by: Dean Rasheed <[email protected]>
Discussion: https://postgr.es/m/aHVWKM8l8kLlZzgv%40nathan
Backpatch-through: 18

diff --git a/doc/src/sgml/pgoverexplain.sgml b/doc/src/sgml/pgoverexplain.sgml
index 21930fbd3bd76ea48143662a3971672c59c2de32..377ddc8139ecf2ef2348f74247a64ed780264583 100644 (file)
--- a/doc/src/sgml/pgoverexplain.sgml
+++ b/doc/src/sgml/pgoverexplain.sgml
@@ -8,7 +8,7 @@
  </indexterm>
 
  <para>
-  The <filename>pg_overexplain</filename> extends <command>EXPLAIN</command>
+  The <filename>pg_overexplain</filename> module extends <command>EXPLAIN</command>
   with new options that provide additional output. It is mostly intended to
   assist with debugging of and development of the planner, rather than for
   general use. Since this module displays internal details of planner data
@@ -17,6 +17,21 @@
   often as) those data structures change.
  </para>
 
+ <para>
+  To use it, simply load it into the server.  You can load it into an
+  individual session:
+
+<programlisting>
+LOAD 'pg_overexplain';
+</programlisting>
+
+  You can also preload it into some or all sessions by including
+  <literal>pg_overexplain</literal> in
+  <xref linkend="guc-session-preload-libraries"/> or
+  <xref linkend="guc-shared-preload-libraries"/> in
+  <filename>postgresql.conf</filename>.
+ </para>
+
  <sect2 id="pgoverexplain-debug">
   <title>EXPLAIN (DEBUG)</title>