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From: Christopher Kings-Lynne <chriskl@familyhealth.com.au>
To: Ken Geis <kgeis@speakeasy.org>
To: Bruno Wolff III <bruno@wolff.to>
Cc: pgsql-performance@postgresql.org
Subject: Re: bad estimates
Date: Fri, 29 Aug 2003 16:15:05 +0800
Message-ID: <0bf301c36e05$a72f90b0$2800a8c0@mars> (raw)
References: <3F4E99F7.7080604@speakeasy.org>
	<20030829025109.GD4373@wolff.to>
	<3F4EBF7E.8020602@speakeasy.org>
	<20030829030156.GF4373@wolff.to>
	<3F4EC1D0.5010503@speakeasy.org>
	<20030829033818.GA5577@wolff.to>
	<3F4ECC78.7090502@speakeasy.org>
	<20030829040519.GA5746@wolff.to>
	<3F4ED1DC.50808@speakeasy.org>
	<20030829042453.GA5931@wolff.to>
	<3F4F0777.8090503@speakeasy.org>
	<3F4F0A5E.8030207@speakeasy.org>

> > I went through the code (7.4 beta2) that estimates the cost of an index
> > scan path.  What I need to be sure of is that when running a query in
> > pgsql that uses only the columns that are in an index, the underlying
> > table need not be accessed.  I know that Oracle does this.

PostgreSQL absolutely does not do this.  It is also not possible to do this
due to MVCC.

Chris




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