From: Jimmy Mäkelä <jimmy.makela@agent25.se>
To: Tomasz Myrta <jasiek@klaster.net>
Cc: 'pgsql-sql@postgresql.org' <pgsql-sql@postgresql.org>
Subject: Re: Unique indexes not unique?
Date: Mon, 13 Jan 2003 11:56:09 +0100
Message-ID: <D1045567F50DD311AB1B00508B3188E9026546D9@RINGHALS> (raw)
From: Tomasz Myrta [mailto:jasiek@klaster.net]
> I'm not sure unique index works properly for null values. I can't
> explain, why. Maybe it comes from SQL standard - null i a
> special value
Yeah, I thought about that too, but I think that behaviour is really bad and
would consider it a bug. There are good reasons for having a special SQL null,
but
none of these apply to unique indexes (not that I can think of anyway).
> Try to rewrite your query to show postgres how to use index on AB:
> SELECT * FROM "table"
> WHERE
> (a = 1 AND b > 1232132 AND b < 123123123213123) or
> (a = 2 AND b > 1232132 AND b < 123123123213123) or
> (a = 3 AND b > 1232132 AND b < 123123123213123);
Sure, this works, and is an improvement to the UNION-version, but I think
postgres should be able do these substitutions by itself in the
planner/optimizer...
Or is there any method for specifying optimizer hints?
Regards,
Jimmy
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Subject: Re: Unique indexes not unique?
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