Re: quickly getting the top N rows - Mailing list pgsql-performance

From Ben
Subject Re: quickly getting the top N rows
Date
Msg-id Pine.LNX.4.64.0710041414590.30864@localhost.localdomain
Whole thread Raw
In response to Re: quickly getting the top N rows  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-performance

On Thu, 4 Oct 2007, Tom Lane wrote:

> There's some limited smarts in there about deciding that leading columns
> of an index don't matter to the sort ordering if they're constrained to
> just one value by the query.  But it doesn't catch the case you need,
> which is that columns of an ORDER BY request are no-ops when they're
> constrained to just one value.

Oh, no, that explains it perfectly, because that's precisely the case I
have - I dropped the columns from the ordering, but not the where clause.
Thanks, now I understand the current behavior.

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