Add some notes about how pg_dump relates to the practices recommended

tglsfdc · tglsfdc · commit 6c0398a73f0a · 2005-09-02T03:19:53.000Z
under 'Populating a Database'.
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/perform.sgml,v 1.52 2005/09/02 00:57:57 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/perform.sgml,v 1.53 2005/09/02 03:19:53 tgl Exp $
 -->
 
  <chapter id="performance-tips">
@@ -878,6 +878,54 @@ SELECT * FROM x, y, a, b, c WHERE something AND somethingelse;
     statistics.
    </para>
   </sect2>
+
+  <sect2 id="populate-pg-dump">
+   <title>Some Notes About <application>pg_dump</></title>
+
+   <para>
+    Dump scripts generated by <application>pg_dump</> automatically apply
+    several, but not all, of the above guidelines.  To reload a
+    <application>pg_dump</> dump as quickly as possible, you need to
+    do a few extra things manually.  (Note that these points apply while
+    <emphasis>restoring</> a dump, not while <emphasis>creating</> it.
+    The same points apply when using <application>pg_restore</> to load
+    from a <application>pg_dump</> archive file.)
+   </para>
+
+   <para>
+    By default, <application>pg_dump</> uses <command>COPY</>, and when
+    it is generating a complete schema-and-data dump, it is careful to
+    load data before creating indexes and foreign keys.  So in this case
+    the first several guidelines are handled automatically.  What is left
+    for you to do is to set appropriate (i.e., larger than normal) values
+    for <varname>maintenance_work_mem</varname> and
+    <varname>checkpoint_segments</varname> before loading the dump script,
+    and then to run <command>ANALYZE</> afterwards.
+   </para>
+
+   <para>
+    A data-only dump will still use <command>COPY</>, but it does not
+    drop or recreate indexes, and it does not normally touch foreign
+    keys.
+
+     <footnote>
+      <para>
+       You can get the effect of disabling foreign keys by using
+       the <option>-X disable-triggers</> option &mdash; but realize that
+       that eliminates, rather than just postponing, foreign key
+       validation, and so it is possible to insert bad data if you use it.
+      </para>
+     </footnote>
+
+    So when loading a data-only dump, it is up to you to drop and recreate
+    indexes and foreign keys if you wish to use those techniques.
+    It's still useful to increase <varname>checkpoint_segments</varname>
+    while loading the data, but don't bother increasing
+    <varname>maintenance_work_mem</varname>; rather, you'd do that while
+    manually recreating indexes and foreign keys afterwards.
+    And don't forget to <command>ANALYZE</> when you're done.
+   </para>
+  </sect2>
   </sect1>
 
  </chapter>
