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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Gavin M. Roy <gmr@myyearbook.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: SQL Function Slowness, 8.3.0
Date: Wed, 16 Apr 2008 16:24:32 -0400
Message-ID: <18099.1208377472@sss.pgh.pa.us> (raw)
In-Reply-To: <af1bce590804161144q1b78be6cy69c9a44cc4b9b7bf@mail.gmail.com>
References: <af1bce590804160806t58f7da1g50fc697dd9e6ab08@mail.gmail.com>
	<8328.1208358587@sss.pgh.pa.us>
	<af1bce590804161144q1b78be6cy69c9a44cc4b9b7bf@mail.gmail.com>

"Gavin M. Roy" <gmr@myyearbook.com> writes:
> After detailed examination of pg_stat_user_indexes usage, it's clear that
> the functions don't use the same indexes.  I've casted everything to match
> the indexes in the SQL function, to no success.  Any suggestions on next
> steps?  Maybe for 8.4 we could find a way to explain analyze function
> internals ;-)

Yeah, this could be easier, but it's certainly possible to examine the
plan generated for a function's parameterized statement.  For instance,
say you're wondering about the plan for

	create function foo(int, text) ... as
	$$ select * from bar where f1 = $1 and f2 = $2 $$
	language sql

What you do is

prepare p(int, text) as select * from bar where f1 = $1 and f2 = $2 ;

explain analyze execute p(42, 'hello world');

It works exactly the same for statements in plpgsql functions,
remembering that both parameters and local variables of the function
have to become $n placeholders.  Remember to make the parameters
of the prepared statement have the same declared types as the
function's parameters and variables.

			regards, tom lane



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