Explain not accurate - Mailing list pgsql-performance

From Richard van den Berg
Subject Explain not accurate
Date
Msg-id 3FFEB6DA.8000905@trust-factory.com
Whole thread Raw
Responses Re: Explain not accurate  (Dennis Bjorklund <db@zigo.dhs.org>)
Re: Explain not accurate  (Christopher Kings-Lynne <chriskl@familyhealth.com.au>)
Re: Explain not accurate  (Greg Stark <gsstark@mit.edu>)
List pgsql-performance
Hi there,

I am quite new to postgresql, and love the explain feature. It enables
us to predict which SQL queries needs to be optimized before we see any
problems. However, I've run into an issue where explain tells us a the
costs of a quiry are tremendous (105849017586), but the query actually
runs quite fast. Even "explain analyze" shows these costs.

This makes me wonder: can the estimates explain shows be dead wrong?

I can explain in more detail (including the query and output of explain)
if needed. I'm using 7.4 on Solaris 8.

Sincerely,

--
Richard van den Berg, CISSP

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