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help / color / mirror / Atom feedFrom: Tom Lane <[email protected]>
To: Robert Haas <[email protected]>
Cc: Simon Riggs <[email protected]>
Cc: Ron Mayer <[email protected]>
Cc: Euler Taveira de Oliveira <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: explain analyze rows=%.0f
Date: Tue, 02 Jun 2009 10:38:27 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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Robert Haas <[email protected]> writes:
> On Jun 2, 2009, at 9:41 AM, Simon Riggs <[email protected]> wrote:
>> You're right that the number of significant digits already exceeds the
>> true accuracy of the computation. I think what Robert wants to see is
>> the exact value used in the calc, so the estimates can be checked more
>> thoroughly than is currently possible.
> Bingo.
Uh, the planner's estimate *is* an integer. What was under discussion
(I thought) was showing some fractional digits in the case where EXPLAIN
ANALYZE is outputting a measured row count that is an average over
multiple loops, and therefore isn't necessarily an integer. In that
case the measured value can be considered arbitrarily precise --- though
I think in practice one or two fractional digits would be plenty.
regards, tom lane
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