Fixed: empty tuple error when select oldest transaction age

Author: Roman Nikolaev

mamonsu/plugins/pgsql/oldest.py

@@ -17,14 +17,17 @@ class Oldest(Plugin):
 """
 
     OldestQuerySql = """
-select
-    extract(epoch from max(now() - xact_start))
-from pg_catalog.pg_stat_activity 
-where 
-    pid not in (select pid from pg_stat_replication)
-    AND pid <> pg_backend_pid() 
-    AND query not ilike '%VACUUM%' 
-    HAVING extract(epoch from max(now() - xact_start))>0;
+SELECT 
+  CASE WHEN extract(epoch from max(now() - xact_start)) IS NOT null 
+    THEN extract(epoch from max(now() - xact_start)) 
+    ELSE 0 
+  END 
+FROM pg_catalog.pg_stat_activity 
+WHERE 
+  pid NOT IN(select pid from pg_stat_replication) AND 
+  pid <> pg_backend_pid() AND 
+  query NOT ilike '%%VACUUM%%' 
+HAVING extract(epoch from max(now() - xact_start))>0;
 """
 
     OldestQuerySql_bootstrap = """

mamonsu/tools/bootstrap/sql.py

@@ -67,14 +67,17 @@
 
 CREATE or REPLACE FUNCTION public.mamonsu_get_oldest_query()
 RETURNS DOUBLE PRECISION AS $$
-    SELECT
-        extract(epoch from max(now() - xact_start))
-    FROM pg_catalog.pg_stat_activity
+    SELECT 
+        CASE WHEN extract(epoch from max(now() - xact_start)) IS NOT null 
+            THEN extract(epoch from max(now() - xact_start)) 
+            ELSE 0 
+        END 
+    FROM pg_catalog.pg_stat_activity 
     WHERE 
-        pid not in (select pid from pg_stat_replication)
-        AND pid <> pg_backend_pid() 
-        AND query not ilike '%VACUUM%' 
-        HAVING extract(epoch from max(now() - xact_start))>0
+        pid NOT IN(select pid from pg_stat_replication) AND 
+        pid <> pg_backend_pid() AND 
+        query NOT ilike '%%VACUUM%%' 
+    HAVING extract(epoch from max(now() - xact_start))>0
 $$ LANGUAGE SQL SECURITY DEFINER;
 
 CREATE OR REPLACE FUNCTION public.mamonsu_count_{3}_files()