From: anthony.shipman@symstream.com
To: pgsql-performance@postgresql.org
Subject: Re: overzealous sorting?
Date: Tue, 27 Sep 2011 12:45:00 +1000
Message-ID: <201109271245.00979.anthony.shipman@symstream.com> (raw)
In-Reply-To: <20110926113901.38fdf892@marco-dalibo>
References: <201109261628.15363.anthony.shipman@symstream.com>
<20110926113901.38fdf892@marco-dalibo>
On Monday 26 September 2011 19:39, Marc Cousin wrote:
> Because Index Scans are sorted, not Bitmap Index Scans, which builds a
> list of pages to visit, to be then visited by the Bitmap Heap Scan step.
>
> Marc.
Where does this bitmap index scan come from? It seems to negate the advantages
of b-tree indexes described in the section "Indexes and ORDER BY" of the
manual. If I do "set enable_bitmapscan = off;" the query runs a bit faster
although with a larger time range it reverts to a sequential scan.
--
Anthony Shipman | Consider the set of blacklists that
Anthony.Shipman@symstream.com | do not blacklist themselves...
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To: pgsql-performance@postgresql.org
Cc: anthony.shipman@symstream.com
Subject: Re: overzealous sorting?
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