Add a metric for tracking the number of granted locks

sample-config/pgmon-metrics.yml

@@ -230,7 +230,19 @@ metrics:
         SELECT COUNT(*) FILTER (WHERE has_sequence_privilege(c.oid, 'SELECT,USAGE')) AS visible_sequences,
                COUNT(*) AS total_sequences
         FROM pg_class AS c
-        WHERE relkind = 'S';
+        WHERE relkind = 'S'
+
+  locks:
+    type: row
+    query:
+      0:
+        SELECT COUNT(*) AS total,
+               SUM(CASE WHEN granted THEN 1 ELSE 0 END) AS granted
+        FROM pg_locks
+      90400: >
+        SELECT COUNT(*) AS total,
+               COUNT(*) FILTER (WHERE granted) AS granted
+        FROM pg_locks
 
 
   ##