Re: postgres chooses objectively wrong index

I've been maintaining an airflow style orchestrator in pl/pgsql, and it's revealed a performance issue I just can't solve.  There is a table, task, which may normally contain billions of rows, but only a tiny portion is interesting for specific reasons—a common pattern in task-type systems.

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I'm wondering if there are other tricks that might apply here, for example, multi column index statistics...curious if anyone has thoughts on that.

Any suggestions?

merlin

Hello. I think planner doesn't have information about distribution of async.task_execution_state(task) unless it's part of any full index. I would try to give that with extended statistics (postgresql 14+):

create statistics (mcv) task_task_execution_state_stat on ((async.task_execution_state(task))) from async.task;
analyze async.task;

If that won't help - please show distribution from pg_stats_ext view for extended statistic above.

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Alexey Ermakov