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 |
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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.
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