Partitions

The other day my team came across a peculiar situation with our Postgres database. We had this table partitioned by a primary key, which we’ll call order_id. We realised one of the queries was taking a very long time to execute, and like good SQL debuggers we looked at the query plan. Let’s pretend this was the slow query: EXPLAIN ANALYZE SELECT * FROM orders WHERE customer_id = 12345; Upon inspection, we observed that the query plan was scanning at every single partition! And in our case, there were a lot of them. ...