Do I need to ANALYZE table after DROP INDEX?

Question

In our postgres db we historically have many similar indexes (e.g. is_deleted boolean) that have quite bad selectivity value. Worse than that, sometimes query planner breaks and postgres starts to use some of them instead of much more efficient indexes so we need to call ANALYZE manually to fix performance, so we decided to delete most of them.

Do we need to call ANALYZE for each table after deleting index?

According to the answer in Is it necessary to ANALYZE a table after an index has been created? postgres collects stats about actual values in table (for simple indexes) without index-related info but I couldn't find proof in docs.

Answer 1

No, it's not necessary. Statistics on the main table are not affected by indexes at all.

One thing to observe: expression indexes introduce new "derived" columns, and Postgres gathers separate statistics for those. Removing such indexes also removes the special statistics - which may lead to different query plans, beyond the fact that the index is gone.

Since you mention indexes on boolean columns: those hardly ever make sense and it's a good idea to remove those. boolean column typically only make sense as condition in a partial index. There is an example in the manual.