PostgreSQL: implementing Recursive CTE when Handling Large Data Sets and Performance Degradation
I recently switched to I'm attempting to set up I'm currently working with a recursive Common Table Expression (CTE) in PostgreSQL 14 to traverse a hierarchical structure stored in a table. The scenario arises when I attempt to query a large dataset containing over 1 million records. The query runs extremely slow, and I often encounter a timeout behavior after 30 seconds. Here's the basic structure of my CTE: ```sql WITH RECURSIVE hierarchy AS ( SELECT id, parent_id, name FROM my_table WHERE parent_id IS NULL UNION ALL SELECT t.id, t.parent_id, t.name FROM my_table t INNER JOIN hierarchy h ON h.id = t.parent_id ) SELECT * FROM hierarchy; ``` I've tried adding indexes on `parent_id` and `id`, but it hasn't improved performance significantly. When I run an EXPLAIN ANALYZE on the query, it shows that the recursive part is taking the majority of the execution time, leading me to believe that the recursive call is not optimized. Additionally, I've attempted to limit the recursion depth by adding a `LIMIT` clause, but that only partially mitigates the scenario. Is there a recommended approach or best practice for optimizing recursive CTEs in PostgreSQL, especially when dealing with large hierarchical datasets? Any tips on tuning queries or alternative strategies would be greatly appreciated. For context: I'm using Sql on Linux. I'm working on a mobile app that needs to handle this. Could someone point me to the right documentation? The project is a REST API built with Sql. The project is a application built with Sql.