Re: Unique indexes not unique?

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