From: | Hannu Krosing <hannu(at)trust(dot)ee> |
---|---|
To: | Olaf Mittelstaedt <mstaedt(at)va-sigi(dot)va(dot)fh-ulm(dot)de> |
Cc: | pgsql-interfaces(at)postgreSQL(dot)org |
Subject: | Re: [INTERFACES] Re: Index unused with OR? |
Date: | 1998-05-14 15:10:02 |
Message-ID: | 355B094A.43F1DAAE@trust.ee |
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Lists: | pgsql-interfaces |
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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