Added support for collecting arbitrary sql queries.

Added metrics for locks per database per mode, pg_stat_activity, pg_stat_replication.
Updated README.md with possible solution for running as non-superuser.

README.md

@@ -41,3 +41,42 @@ for l in StringIO(x):
 ```
 Adjust the value of the resultant prometheus value type appropriately. This helps build
 rich self-documenting metrics for the exporter.
+
+
+### Running as non-superuser
+
+To be able to collect metrics from pg_stat_activity and pg_stat_replication as non-superuser you have to create functions and views to do so.
+
+```sql
+CREATE USER postgres_exporter PASSWORD 'password';
+ALTER USER postgres_exporter SET SEARCH_PATH TO postgres_exporter,pg_catalog;
+
+CREATE SCHEMA postgres_exporter AUTHORIZATION postgres_exporter;
+
+CREATE FUNCTION postgres_exporter.f_select_pg_stat_activity()
+RETURNS setof pg_catalog.pg_stat_activity
+LANGUAGE sql
+SECURITY DEFINER
+AS $$
+  SELECT * from pg_catalog.pg_stat_activity;
+$$;
+
+CREATE FUNCTION postgres_exporter.f_select_pg_stat_replication()
+RETURNS setof pg_catalog.pg_stat_replication
+LANGUAGE sql
+SECURITY DEFINER
+AS $$
+  SELECT * from pg_catalog.pg_stat_replication;
+$$;
+
+CREATE VIEW postgres_exporter.pg_stat_replication
+AS
+  SELECT * FROM postgres_exporter.f_select_pg_stat_replication();
+
+CREATE VIEW postgres_exporter.pg_stat_activity
+AS
+  SELECT * FROM postgres_exporter.f_select_pg_stat_activity();
+
+GRANT SELECT ON postgres_exporter.pg_stat_replication TO postgres_exporter;
+GRANT SELECT ON postgres_exporter.pg_stat_activity TO postgres_exporter;
+```