From: | Mario Splivalo <mario(dot)splivalo(at)megafon(dot)hr> |
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To: | pgsql-performance(at)postgresql(dot)org |
Cc: | pgsql-jdbc(at)postgresql(dot)org |
Subject: | Re: [PERFORM] Query much slower when run from postgres function |
Date: | 2009-03-09 19:26:05 |
Message-ID: | 49B56D4D.9090605@megafon.hr |
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Thread: | |
Lists: | pgsql-jdbc pgsql-performance |
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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