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Re: Querying distinct values from a large table

From: "Chad Wagner" <chad(dot)wagner(at)gmail(dot)com>
To: "Luke Lonergan" <llonergan(at)greenplum(dot)com>
Cc: "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Igor Lobanov" <ilobanov(at)swsoft(dot)com>, "Richard Huxton" <dev(at)archonet(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Querying distinct values from a large table
Date: 2007-01-30 15:03:03
Message-ID: 81961ff50701300703r538cfd58o511ef68ee90a90e5@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On 1/30/07, Luke Lonergan <llonergan(at)greenplum(dot)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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