From: Chad Wagner <chad.wagner@gmail.com>
To: Luke Lonergan <llonergan@greenplum.com>
Cc: Simon Riggs <simon@2ndquadrant.com>
Cc: Igor Lobanov <ilobanov@swsoft.com>
Cc: Richard Huxton <dev@archonet.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Querying distinct values from a large table
Date: Tue, 30 Jan 2007 10:03:03 -0500
Message-ID: <81961ff50701300703r538cfd58o511ef68ee90a90e5@mail.gmail.com> (raw)
In-Reply-To: <C1E49CB9.199A4%llonergan@greenplum.com>
References: <81961ff50701300613g25ea4ce6jb357c82fb1ed6733@mail.gmail.com>
<C1E49CB9.199A4%llonergan@greenplum.com>
On 1/30/07, Luke Lonergan <llonergan@greenplum.com> wrote:
>
> Not that it helps Igor, but we've implemented single pass sort/unique,
> grouping and limit optimizations and it speeds things up to a single
> seqscan
> over the data, from 2-5 times faster than a typical external sort.
Was that integrated back into PostgreSQL, or is that part of Greenplum's
offering?
I can't think of a way that indexing would help this situation given the
> required visibility check of each tuple.
>
I agree, using indexes as a "skinny" table is a whole other feature that
would be nice.
--
Chad
http://www.postgresqlforums.com/
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To: pgsql-performance@postgresql.org
Cc: chad.wagner@gmail.com, llonergan@greenplum.com, simon@2ndquadrant.com, ilobanov@swsoft.com, dev@archonet.com
Subject: Re: Querying distinct values from a large table
In-Reply-To: <81961ff50701300703r538cfd58o511ef68ee90a90e5@mail.gmail.com>
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