Add note that inlined SQL functions aren't tracked by track_functions.

doc/src/sgml/config.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.208 2009/02/15 18:28:48 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.209 2009/02/22 23:50:30 tgl Exp $ -->
 
 <chapter Id="runtime-config">
   <title>Server Configuration</title>
@@ -3361,11 +3361,19 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       <listitem>
        <para>
         Enables tracking of function call counts and time used. Specify
-        <literal>pl</literal> to count only procedural language functions,
+        <literal>pl</literal> to track only procedural-language functions,
         <literal>all</literal> to also track SQL and C language functions.
-        The default is <literal>none</literal>.
-        Only superusers can change this setting.
+        The default is <literal>none</literal>, which disables function
+        statistics tracking.  Only superusers can change this setting.
        </para>
+
+       <note>
+        <para>
+         SQL-language functions that are simple enough to be <quote>inlined</>
+         into the calling query will not be tracked, regardless of this
+         setting.
+        </para>
+       </note>
       </listitem>
      </varlistentry>