Re: increasing effective_cache_size slows down join queries by a factor of 4000x

From: Artyom Shaposhnikov <artyom(at)gmail(dot)com>
To: Michael Lewis <mlewis(at)entrata(dot)com>
Cc: pgsql-general(at)lists(dot)postgresql(dot)org
Subject: Re: increasing effective_cache_size slows down join queries by a factor of 4000x
Date: 2022-02-02 21:10:27
Message-ID: CA+1Wm9XwEBvdUHWQawmji_Z4wMbCzfvqgmYg0QDMkR5Q_LtikA@mail.gmail.com
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the row estimate became ~1000x smaller with the stat in place, so it
looks like it grossly miscalculates the query plans without the stats
for large tables representing M:M relations.

On Wed, Feb 2, 2022 at 11:47 AM Michael Lewis <mlewis(at)entrata(dot)com> wrote:
>
> What does the row estimate look like on the scan of data table with that statistic in place? Anytime the stats give a mis-estimate this far off, I wouldn't expect that plans would be optimal except by luck.
>
> Index Scan using data_pkey on data t (cost=0.57..21427806.53 rows=58785023 width=131) (actual time=0.024..0.482 rows=854 loops=1)
> Index Cond: (id > 205284974)

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