strange slow query - lost lot of time somewhere

Pavel Stehule <pavel.stehule@gmail.com>

From: Pavel Stehule <pavel.stehule@gmail.com>

To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2022-05-02T08:59:33Z

Lists: pgsql-hackers

Hi

I found a query that is significantly slower with more memory

plan 1 - fast https://explain.depesz.com/s/XM1f

plan 2 - slow https://explain.depesz.com/s/2rBw

Strange - the time of last row is +/- same, but execution time is 10x worse

It looks like slow environment cleaning

Commits

Correct Memoize's estimated cache hit ratio calculation
- f48b4f892f76 16.0 landed
Fix incorrect row estimates used for Memoize costing
- 23c2b76a8322 14.4 landed
- 1e731ed12aac 15.0 landed
Allow Memoize to operate in binary comparison mode
- 6c32c0977783 14.2 cited