Re: [PERFORM] Query much slower when run from postgres function

From: Mario Splivalo
Subject: Re: [PERFORM] Query much slower when run from postgres function
Date: ,
Msg-id: 49B56D4D.9090605@megafon.hr
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In response to: Re: [PERFORM] Query much slower when run from postgres function  (Guillaume Cottenceau)
List: pgsql-jdbc

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Re: [PERFORM] Query much slower when run from postgres function  (Guillaume Cottenceau, )
 Re: [PERFORM] Query much slower when run from postgres function  (Guillaume Smet, )
  Re: [PERFORM] Query much slower when run from postgres function  (Tom Lane, )
   Re: [PERFORM] Query much slower when run from postgres function  (Andreas Wenk, )
   Re: [PERFORM] Query much slower when run from postgres function  (Dave Cramer, )
    Re: [PERFORM] Query much slower when run from postgres function  (James Mansion, )
    Re: [PERFORM] Query much slower when run from postgres function  (Oliver Jowett, )
     Re: [PERFORM] Query much slower when run from postgres function  (Guillaume Cottenceau, )
      Re: [PERFORM] Query much slower when run from postgres function  (Oliver Jowett, )
       Re: [PERFORM] Query much slower when run from postgres function  (Guillaume Cottenceau, )
        Re: [PERFORM] Query much slower when run from postgres function  (Kris Jurka, )
  Re: [PERFORM] Query much slower when run from postgres function  (Scott Carey, )
   Re: [PERFORM] Query much slower when run from postgres function  (Oliver Jowett, )
    Re: [PERFORM] Query much slower when run from postgres function  (Scott Carey, )
 Re: [PERFORM] Query much slower when run from postgres function  (Mario Splivalo, )

Guillaume Cottenceau wrote:
>>> Now I'm confused, why is 'sql' function much slower than 'direct' SELECT?
>> Usually the reason for this is that the planner chooses a different plan
>> when it has knowledge of the particular value you are searching for than
>> when it does not.
>
> Yes, and since Mario is coming from JDBC, I'll share my part on
> this: I also noticed some very wrong plans in JDBC because of the
> "optimization" in prepared statements consisting of planning once
> for all runs, e.g. without any parameter values to help planning.
>

For what is worth:

When I call postgres function via JDBC, I have almost the same execution
time as when calling function from psql.

When I call SELECT COUNT(*)... WHERE... query from JDBC, I again have
almost the same execution time as when executing query from psql.

Postgres function takes around 200ms, and SELECT query takes around 2-4ms.

    Mike


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