From: Heikki Linnakangas <heikki@enterprisedb.com>
To: alvherre@commandprompt.com, Guillaume Cottenceau <gc@mnc.ch>
To: pgsql-performance@postgresql.org
Subject: Re: Poor performance on seq scan
Date: Tue, 12 Sep 2006 14:45:06 +0100
Message-ID: <4506B9E2.9050608@enterprisedb.com> (raw)
In-Reply-To: <20060912133254.GC11324@alvh.no-ip.org>
References: <450684EC.4090304@designaproduct.biz>
<4506902C.7090407@enterprisedb.com>
<4506A9E7.2060303@designaproduct.biz>
<87y7spw8v9.fsf@meuh.mnc.lan>
<4506B508.80806@enterprisedb.com>
<20060912133254.GC11324@alvh.no-ip.org>
Alvaro Herrera wrote:
> Are you saying that an indexscan "Filter" only acts after getting the
> heap tuple? If that's the case, then there's room for optimization
> here, namely if the affected column is part of the index key, then we
> could do the filtering before fetching the heap tuple.
That's right. Yes, there's definitely room for optimization. In general,
it seems we should detach the index scan and heap fetch more. Perhaps
make them two different nodes, like the bitmap index scan and bitmap
heap scan. It would allow us to do the above. It's also going to be
necessary if we ever get to implement index-only scans.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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To: pgsql-performance@postgresql.org
Cc: heikki@enterprisedb.com, gc@mnc.ch
Subject: Re: Poor performance on seq scan
In-Reply-To: <4506B9E2.9050608@enterprisedb.com>
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