Re: increasing effective_cache_size slows down join queries by a factor of 4000x - Mailing list pgsql-general

From Artyom Shaposhnikov
Subject Re: increasing effective_cache_size slows down join queries by a factor of 4000x
Date
Msg-id CA+1Wm9XwEBvdUHWQawmji_Z4wMbCzfvqgmYg0QDMkR5Q_LtikA@mail.gmail.com
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In response to Re: increasing effective_cache_size slows down join queries by a factor of 4000x  (Michael Lewis <mlewis@entrata.com>)
Responses Re: increasing effective_cache_size slows down join queries by a factor of 4000x  (Tomas Vondra <tomas.vondra@enterprisedb.com>)
List pgsql-general
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@entrata.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-estimatethis 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=854loops=1)
 
> Index Cond: (id > 205284974)



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