Date: Sat, 18 Feb 2012 17:02:44 +0100
From: Andreas Kretschmer <akretschmer@spamfence.net>
To: pgsql-performance@postgresql.org
Subject: Re: Query slow as Function
Message-ID: <20120218160244.GA23315@tux>
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Steve Horn <steve@stevehorn.cc> wrote:

> Execute the function: select * from geocode_carrier_route_by_geocode('xyz');
> 
> This query takes 500 milliseconds to run. My question of course is why?

Wild guess:

The planner doesn't know the actual value of the input-parameter, so the
planner doesn't use the Index.

> 
> Related: If I create a function and assign LANGUAGE 'sql', my function runs in
> the expected 10 milliseconds. Is there some overhead to using the plpgsql
> language?

The planner, in this case, knows the actual value.

> 
> Thanks for any help in clarifying my understanding!

You can check the plan with the auto_explain - Extension, and you can
force the planner to create a plan based on the actual input-value by
using dynamic SQL (EXECUTE 'your query string' inside the function)


As i said, wild guess ...


Andreas
-- 
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