Re: Choice of bitmap scan over index scan

From: Jeremy Harris <jgh(at)wizmail(dot)org>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Choice of bitmap scan over index scan
Date: 2010-01-10 14:04:47
Message-ID: 4B49DE7F.8080808@wizmail.org
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On 01/10/2010 12:28 PM, Mathieu De Zutter wrote:
>Sort (cost=481763.31..485634.61 rows=1548520 width=338) (actual time=5423.628..6286.148 rows=1551923 loops=1)
> Sort Key: event_timestamp
> Sort Method: external merge Disk: 90488kB
> -> Seq Scan on log_event (cost=0.00..79085.92 rows=1548520 width=338) (actual time=0.022..2195.527 rows=1551923 loops=1)
> Filter: (event_timestamp > (now() - '1 year'::interval))
> Total runtime: 6407.377 ms

Needing to use an external (on-disk) sort method, when taking
only 90MB, looks odd.

- Jeremy

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