👀 Views: 301 💬 Answers: 1 📅 Created: 2025-06-11

postgresql sql cte

I'm performance testing and I'm currently working with a recursive Common Table Expression (CTE) in PostgreSQL 13.3 to traverse a hierarchical structure in my database... However, I'm experiencing unexpected behavior where the query runs indefinitely, leading to a potential infinite loop. Here’s the CTE I’m using: ```sql WITH RECURSIVE org_chart AS ( SELECT id, name, manager_id FROM employees WHERE manager_id IS NULL -- Start from the top level UNION ALL SELECT e.id, e.name, e.manager_id FROM employees e JOIN org_chart oc ON e.manager_id = oc.id -- Recursive join ) SELECT * FROM org_chart; ``` The `employees` table has a structure like this: ```sql CREATE TABLE employees ( id SERIAL PRIMARY KEY, name VARCHAR(100), manager_id INT REFERENCES employees(id) ); ``` I’ve verified that there are no circular references in the `manager_id` field, but I still suspect there's something I'm overlooking. To troubleshoot, I tried limiting the recursion depth with `LIMIT`, but that resulted in incomplete data: ```sql WITH RECURSIVE org_chart AS ( SELECT id, name, manager_id FROM employees WHERE manager_id IS NULL UNION ALL SELECT e.id, e.name, e.manager_id FROM employees e JOIN org_chart oc ON e.manager_id = oc.id ) SELECT * FROM org_chart LIMIT 100; ``` I'm not sure if I'm misunderstanding how recursion works in CTEs or if there's something else causing this issue. The query just keeps running without finishing, and I’ve even tried analyzing the execution plan, which doesn’t seem to show anything abnormal. Any insights on how to avoid this infinite loop or better handle recursion in CTEs would be greatly appreciated! Is there a better approach?