added truncate instead of delete (tembo-io#321)

* added truncate instead of delete

Signed-off-by: Abinand P <abinand0911@gmail.com>

* updated and resolved the function name to get the table

---------

Signed-off-by: Abinand P <abinand0911@gmail.com>

pgmq-extension/sql/pgmq.sql

@@ -378,18 +378,24 @@ END
 $$ LANGUAGE plpgsql;
 
 -- purge queue, deleting all entries in it.
-CREATE FUNCTION pgmq."purge_queue"(queue_name TEXT)
+CREATE OR REPLACE FUNCTION pgmq."purge_queue"(queue_name TEXT)
 RETURNS BIGINT AS $$
 DECLARE
   deleted_count INTEGER;
   qtable TEXT := pgmq.format_table_name(queue_name, 'q');
 BEGIN
-  EXECUTE format('DELETE FROM pgmq.%I', qtable);
-  GET DIAGNOSTICS deleted_count = ROW_COUNT;
+  -- Get the row count before truncating
+  EXECUTE format('SELECT count(*) FROM pgmq.%I', qtable) INTO deleted_count;
+
+  -- Use TRUNCATE for better performance on large tables
+  EXECUTE format('TRUNCATE TABLE pgmq.%I', qtable);
+
+  -- Return the number of purged rows
   RETURN deleted_count;
 END
 $$ LANGUAGE plpgsql;
 
+
 -- unassign archive, so it can be kept when a queue is deleted
 CREATE FUNCTION pgmq."detach_archive"(queue_name TEXT)
 RETURNS VOID AS $$