From: Achilleas Mantzios <achill@matrix.gatewaynet.com>
Organization: Dynacom Tankers Mgmt
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
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=CE=A3=CF=84=CE=B9=CF=82 Friday 21 January 2011 22:22:24 =CE=BF/=CE=B7 Tom =
Lane =CE=AD=CE=B3=CF=81=CE=B1=CF=88=CE=B5:
> "Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> > Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> If it should be less than 1, then what?
> =20
> > 1 - (estimated tuples / estimated distinct values) ?
>=20
> 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)=20
=3D 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

>=20
> 			regards, tom lane
>=20


=2D-=20
Achilleas Mantzios