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Re: Same query, same data different plan - Mailing list pgsql-general

From Imre Samu
Subject Re: Same query, same data different plan
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Msg-id CAJnEWwnm+zCibMcfBV=5CpE0TzY8Gss+RQ8PTcEL8iFhV4igPw@mail.gmail.com
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In response to Same query, same data different plan  (Kostas Papadopoulos <kostas@methodosit.com.cy>)
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> Ran analyze on both. Running the same query I'm getting different plans, one x10 slower.

theory:

the "statistics target" is too low ? 
THEN 
different random sample  --> different statistics ---> different plan,.

"For large tables, ANALYZE takes a random sample of the table contents, rather than examining every row. "

IMHO:  Try to increase the statistics target   ( "default_statistics_target" , .. )

regards,
  Imre

Kostas Papadopoulos <kostas@methodosit.com.cy> ezt írta (időpont: 2022. okt. 10., H, 14:56):

I have two identical databases running in the same instance of Postgresql. Ran
analyze on both. Running the same query I'm getting different plans, one x10 slower.
Although I have solved my problem by re-writing the query, I want to understand why
this is happening. If the configuration, Postgresql version, schema and data are the
same, what other factors is the planner considering?

--

Kostas Papadopoulos
KE MethodosIT



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