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Forcing using index instead of sequential scan?

From: <robin(dot)c(dot)smith(at)bt(dot)com>
To: <pgsql-performance(at)postgresql(dot)org>
Subject: Forcing using index instead of sequential scan?
Date: 2006-07-21 10:40:33
Message-ID: D012B9600FFB984AB18C0D53C475A4A081F51B@E03MVZ3-UKDY.domain1.systemhost.net (view raw or flat)
Thread:
Lists: pgsql-performance
I have been testing the performance of PostgreSQL using the simple tool
found at http://benchw.sourceforge.net however I have found that all the
queries it run execute with sequential scans. The website where the code
runs has examples of the execution plan using indexes.

When I disable the sequential plan query 0 and query 1 run faster (
http://benchw.sourceforge.net/benchw_results_postgres_history.html ) by
using the indexes as suggested by the website.

I have tried increasing the effective_cache_size and reducing the
random_page_cost to try and force the optimiser to use the index but it
always uses the sequential scan.

What is the best way to force the use of indexes in these queries?
Currently testing with version 8.1.4.

Regards

Robin Smith

British Telecommunications plc     Registered office: 81 Newgate Street
London EC1A 7AJ

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Next:From: Peter EisentrautDate: 2006-07-21 11:45:41
Subject: Re: Forcing using index instead of sequential scan?
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Subject: Re: Sun Donated a Sun Fire T2000 to the PostgreSQL

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