Re: Query runs fast or slow

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: felix-accts-pgsql(at)crowfix(dot)com
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Query runs fast or slow
Date: 2006-04-16 20:32:25
Message-ID: 18620.1145219545@sss.pgh.pa.us
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felix-accts-pgsql(at)crowfix(dot)com writes:
> EXPLAIN ANALYZE doesn't show the slow timing
> because it requires values, not $n placeholders,

To analyze the plan used for a parameterized query, try

PREPARE foo(...) AS SELECT ... $n ...

EXPLAIN ANALYZE EXECUTE foo(...)

But I already know what you're going to find: the planner's estimates
for the range query are not going to be very good when it has no idea
what the range bounds are. This is a situation where it may be best
to absorb the hit of re-planning each time instead of using a generic
parameterized plan.

regards, tom lane

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