From: Hannu Krosing <hannu@trust.ee>
To: Olaf Mittelstaedt <mstaedt@va-sigi.va.fh-ulm.de>
Cc: pgsql-interfaces@postgreSQL.org
Subject: Re: [INTERFACES] Re: Index unused with OR?
Date: Thu, 14 May 1998 18:10:02 +0300
Message-ID: <355B094A.43F1DAAE@trust.ee> (raw)
References: <199805141321.PAA04595@gate.va.fh-ulm.de>
<199805141359.PAA04711@gate.va.fh-ulm.de>
Olaf Mittelstaedt wrote:
This is probably the wrong list, but ...
> Actually, I discovered the problem using a table containg more than
> 8000 rows, using the latest release 6.3.2.
>
> > Not using the index in OR queries was some-time ago a bug in
> > PostgreSQL 6.1 if my memory is good. Think that has been solved in
> > new releases, am I wrong ?
seems _not_ to be fixed :(
> VACUUM
> w=> explain select * from p where m = 29000;
> NOTICE: QUERY PLAN:
>
> Index Scan on p (cost=0.00 size=0 width=10)
>
> EXPLAIN
> w=> explain select * from p where (m=29000) or (m=30000);
> NOTICE: QUERY PLAN:
>
> Seq Scan on p (cost=0.00 size=0 width=10)
>
As a work-around try
select * from p where (m=29000) union select * from p where (m=30000);
it should be much faster.
Btw, EXPLAIN thinks this to cost nothing ;)
Unique (cost=0.00 size=0 width=0)
-> Sort (cost=0.00 size=0 width=0)
-> Append (cost=0.00 size=0 width=0)
Hannu
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To: pgsql-interfaces@postgresql.org
Cc: hannu@trust.ee, mstaedt@va-sigi.va.fh-ulm.de
Subject: Re: [INTERFACES] Re: Index unused with OR?
In-Reply-To: <355B094A.43F1DAAE@trust.ee>
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