Add example of how to generate the session identifier from pg_stat_activity.

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index ec954b0304bbff39292adfd2bac20ba39be32a94..c0dada727a508a86de000037f002a70b8a5c0ee2 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1,4 +1,4 @@
-
+
 
 
   Server Configuration
@@ -3088,7 +3088,14 @@ local0.*    /var/log/postgresql
          consisting of two 4-byte hexadecimal numbers (without leading zeros)
          separated by a dot.  The numbers are the process start time and the
          process ID, so %c can also be used as a space saving way
-         of printing those items.
+         of printing those items.  For example, to generate the session
+         identifier from pg_stat_activity, use:
+
+SELECT to_hex(EXTRACT(EPOCH FROM backend_start)::integer) || '.' ||
+       to_hex(procpid)
+FROM pg_stat_activity;
+
+