Re: getting estimated cost to agree with actual

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com>
Cc: "Justin" <justin(at)emproshunts(dot)com>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: getting estimated cost to agree with actual
Date: 2008-06-03 01:20:10
Message-ID: 87mym3iab9.fsf@oxford.xeocode.com
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"Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com> writes:

> On Mon, Jun 2, 2008 at 3:43 PM, Justin <justin(at)emproshunts(dot)com> wrote:
>>
>> I have noticed that estimated Cost to do the query is way off from Actual.
>
> Well, they're not measured in the same units. estimated costs are in
> terms of the cost to sequentially scan a single tuple, while actual
> costs are in milliseconds.

s/tuple/page/

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's On-Demand Production Tuning

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