--- a/postgres.rst	Thu Jan 03 22:03:33 2019 +0200
+++ b/postgres.rst	Thu Jan 03 22:04:43 2019 +0200
@@ -89,6 +89,9 @@
 
    select * from pg_stat_activity;
 
+https://www.postgresql.org/docs/current/monitoring-stats.html
+  The Statistics Collector.
+
 Profile queries
 ===============