PostgreSQL: Index not being used for complex query with CTE and ORDER BY
I'm reviewing some code and I've looked through the documentation and I'm still confused about I'm working with an scenario in PostgreSQL 13.3 where a complex query with a Common Table Expression (CTE) is not utilizing the index on the column I'm filtering. My query looks something like this: ```sql WITH filtered_data AS ( SELECT id, name, created_at FROM my_table WHERE status = 'active' ) SELECT * FROM filtered_data ORDER BY created_at DESC; ``` I've indexed the `created_at` column on `my_table` to improve performance. However, when I run `EXPLAIN ANALYZE`, it shows that a sequential scan is being used instead of using the index. The index was created with the following command: ```sql CREATE INDEX idx_created_at ON my_table (created_at); ``` To troubleshoot, I've tried analyzing the table with `ANALYZE my_table` to update the statistics, but the query plan still shows that the index isn't being used. I also attempted to simplify the query by removing the CTE, but that didn't resolve the scenario either. Additionally, I've checked if there are any conflicting settings in my `postgresql.conf` file, specifically around `random_page_cost`, but it appears to be set to the default value of 4.0. I'm wondering if there are specific conditions under which PostgreSQL decides not to use an index, especially with the use of CTEs. Any insights or solutions on how to force the query to use the index would be greatly appreciated! I'm working with Sql in a Docker container on Windows 10. Is there a better approach?