PostgreSQL Query Optimization with Large Joins Leading to Unexpected Timeouts
I'm integrating two systems and I've searched everywhere and can't find a clear answer. I'm working on a personal project and I'm working with timeouts on a specific query in PostgreSQL 13.4 that involves joining three large tables with millions of rows. The query executes fine for smaller datasets, but when the data scales up, it often results in a timeout behavior: ``` behavior: canceling statement due to statement timeout ``` Here's the query I’m trying to optimize: ```sql SELECT a.id, b.name, c.description FROM table_a AS a JOIN table_b AS b ON a.b_id = b.id JOIN table_c AS c ON a.c_id = c.id WHERE b.active = TRUE AND c.created_at > '2023-01-01'; ``` I've created indexes on the foreign keys and the `active` and `created_at` columns, but it doesn’t seem to help much. The index creation looked like this: ```sql CREATE INDEX idx_table_b_active ON table_b(active); CREATE INDEX idx_table_c_created_at ON table_c(created_at); CREATE INDEX idx_table_a_b_id ON table_a(b_id); CREATE INDEX idx_table_a_c_id ON table_a(c_id); ``` I've also tried increasing the `statement_timeout` configuration to 5 minutes, but it still fails. Running `EXPLAIN ANALYZE` on the query shows that the join between `table_a` and `table_b` is where most of the time is being spent, and it’s doing a sequential scan. Additionally, I’ve attempted to break down the query into multiple smaller queries and then combine the results in the application layer, but that hasn’t improved the performance significantly either. Is there something I might be missing regarding indexing or query structure? Any recommendations for further optimization or alternative approaches would be greatly appreciated! What's the best practice here? Any ideas what could be causing this? What's the best practice here?