From: Achilleas Mantzios <achill@matrix.gatewaynet.com>
To: pgsql-performance@postgresql.org
Subject: Re: "NOT IN" substantially slower in 9.0.2 than 8.3.13 - NOT EXISTS runs fast in both 8.3.13 and 9.0.2
Date: Mon, 24 Jan 2011 17:40:40 +0200
Message-ID: <201101241740.40868.achill@matrix.gatewaynet.com> (raw)
In-Reply-To: <19623.1295641344@sss.pgh.pa.us>
References: <955263366.48014741295283147090.JavaMail.root@ucimail4.uci.cu>
<4D39918C02000025000399DE@gw.wicourts.gov>
<19623.1295641344@sss.pgh.pa.us>
Στις Friday 21 January 2011 22:22:24 ο/η Tom Lane έγραψε:
> "Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> > Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> If it should be less than 1, then what?
>
> > 1 - (estimated tuples / estimated distinct values) ?
>
> Uh, no. The number we're after is the probability that an outer tuple
> has at least one unequal value in the inner relation. This is not 1
> minus the probability that a *specific* inner value is equal, which is
> what I think your formula is estimating.
Isn't this probablity (an outer tuple has at least one unequal value in the inner relation)
= 1 - (probability that all values in the inner relation are equal to the value of the outer tuple)
Anyways, glad to see smth came out of this.
Thx
>
> regards, tom lane
>
--
Achilleas Mantzios
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To: pgsql-performance@postgresql.org
Cc: achill@matrix.gatewaynet.com
Subject: Re: "NOT IN" substantially slower in 9.0.2 than 8.3.13 - NOT EXISTS runs fast in both 8.3.13 and 9.0.2
In-Reply-To: <201101241740.40868.achill@matrix.gatewaynet.com>
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