prevent deadlocks on run_maintenance

sql/functions/run_maintenance.sql

@@ -3,6 +3,7 @@ CREATE FUNCTION @[email protected]_maintenance(
     -- If these defaults change reflect them in `run_maintenance_proc`!
     , p_analyze boolean DEFAULT false
     , p_jobmon boolean DEFAULT true
+    , p_lock_parent boolean DEFAULT false
 )
     RETURNS void
     LANGUAGE plpgsql
@@ -225,6 +226,12 @@ LOOP
 
         -- Loop through child tables starting from highest to get a timestamp from the highest non-empty partition in the set
         -- Avoids doing a scan on entire partition set and/or getting any values accidentally in default.
+        -- Lock the parent_table first to prevent deadlocks
+        IF p_lock_parent THEN
+            RAISE DEBUG 'PERFORM LOCK ONLY %.%', v_parent_schema, v_parent_tablename;
+            PERFORM format('LOCK ONLY ''%I.%I''::regclass IN SHARE UPDATE EXCLUSIVE mode', v_parent_schema, v_parent_tablename);
+        END IF;
+
         FOR v_row_max_time IN
             SELECT partition_schemaname, partition_tablename FROM @[email protected]_partitions(v_row.parent_table, 'DESC', false)
         LOOP
@@ -354,6 +361,12 @@ LOOP
         -- Must be reset to null otherwise if the next partition set in the loop is empty, the previous partition set's value could be used
         v_current_partition_id := NULL;
 
+        -- Lock the parent_table first to prevent deadlocks
+        IF p_lock_parent THEN
+            RAISE DEBUG 'PERFORM LOCK ONLY %.%', v_parent_schema, v_parent_tablename;
+            PERFORM format('LOCK ONLY ''%I.%I''::regclass IN SHARE UPDATE EXCLUSIVE mode', v_parent_schema, v_parent_tablename);
+        END IF;
+
         FOR v_row_max_id IN
             SELECT partition_schemaname, partition_tablename FROM @[email protected]_partitions(v_row.parent_table, 'DESC', false)
         LOOP

sql/procedures/run_maintenance_proc.sql

@@ -3,6 +3,7 @@ CREATE PROCEDURE @[email protected]_maintenance_proc(
     -- Keep these defaults in sync with `run_maintenance`!
     , p_analyze boolean DEFAULT false
     , p_jobmon boolean DEFAULT true
+    , p_lock_parent boolean DEFAULT true
 )
     LANGUAGE plpgsql
     AS $$
@@ -35,8 +36,8 @@ LOOP
 /*
  * Run maintenance with a commit between each partition set
  */
-    v_sql := format('SELECT %s.run_maintenance(%L, p_jobmon := %L',
-        '@extschema@', v_parent_table, p_jobmon);
+    v_sql := format('SELECT %s.run_maintenance(%L, p_jobmon := %L, p_lock_parent := %L',
+        '@extschema@', v_parent_table, p_jobmon, p_lock_parent);
 
     IF p_analyze IS NOT NULL THEN
         v_sql := v_sql || format(', p_analyze := %L', p_analyze);