Add pg_file_settings view and function

The function and view added here provide a way to look at all settings
in postgresql.conf, any #include'd files, and postgresql.auto.conf
(which is what backs the ALTER SYSTEM command).

The information returned includes the configuration file name, line
number in that file, sequence number indicating when the parameter is
loaded (useful to see if it is later masked by another definition of the
same parameter), parameter name, and what it is set to at that point.
This information is updated on reload of the server.

This is unfiltered, privileged, information and therefore access is
restricted to superusers through the GRANT system.

Author: Sawada Masahiko, various improvements by me.
Reviewers: David Steele

1 files changed, 78 insertions, 0 deletions

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 4b79958b357..2756652be21 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -7560,6 +7560,11 @@
      </row>
 
      <row>
+      <entry><link linkend="view-pg-file-settings"><structname>pg_file_settings</structname></link></entry>
+      <entry>file location of parameter settings</entry>
+     </row>
+
+     <row>
       <entry><link linkend="view-pg-shadow"><structname>pg_shadow</structname></link></entry>
       <entry>database users</entry>
      </row>
@@ -9173,6 +9178,79 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
 
  </sect1>
 
+ <sect1 id="view-pg-file-settings">
+  <title><structname>pg_file_settings</structname></title>
+
+  <indexterm zone="view-pg-file-settings">
+   <primary>pg_file_settings</primary>
+  </indexterm>
+
+  <para>
+   The view <structname>pg_file_settings</structname> provides the file
+   name, line number and value of all parameters which are set through
+   configuration files.
+   In contrast to <structname>pg_settings</structname>, a row is provided for
+   each occurrence of the parameter across all configuration files. This is helpful
+   for discovering why one value may have been used in preference to another
+   when the parameters were loaded.
+  </para>
+
+  <table>
+   <title><structname>pg_file_settings</> Columns</title>
+
+  <tgroup cols="3">
+   <thead>
+    <row>
+     <entry>Name</entry>
+     <entry>Type</entry>
+     <entry>Description</entry>
+    </row>
+   </thead>
+   <tbody>
+    <row>
+     <entry><structfield>sourcefile</structfield></entry>
+     <entry><structfield>text</structfield></entry>
+     <entry>Path to and name of the configration file</entry>
+    </row>
+    <row>
+     <entry><structfield>sourceline</structfield></entry>
+     <entry><structfield>integer</structfield></entry>
+     <entry>
+      Line number within the configuration file where the value was set
+     </entry>
+    </row>
+    <row>
+     <entry><structfield>seqno</structfield></entry>
+     <entry><structfield>integer</structfield></entry>
+     <entry>Order in which the setting was loaded</entry>
+    </row>
+    <row>
+     <entry><structfield>name</structfield></entry>
+     <entry><structfield>text</structfield></entry>
+     <entry>Run-time configuration parameter name</entry>
+    </row>
+    <row>
+     <entry><structfield>setting</structfield></entry>
+     <entry><structfield>text</structfield></entry>
+     <entry>value of the parameter</entry>
+    </row>
+   </tbody>
+  </tgroup>
+ </table>
+
+  <para>
+   See <xref linkend="config-setting"> for more information about the various
+   ways to change these parameters.
+  </para>
+
+  <para>
+   The <structname>pg_file_settings</structname> view cannot be modified
+   directly as it represents information, as read in at server start or
+   reload time, about all parameter settings across all configuration files.
+  </para>
+
+</sect1>
+
  <sect1 id="view-pg-shadow">
   <title><structname>pg_shadow</structname></title>