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Re: why is a constraint not 'pushed down' into a subselect when this subselect is using a 'group by' ??

From: Frank van Vugt <ftm(dot)van(dot)vugt(at)foxi(dot)nl>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: why is a constraint not 'pushed down' into a subselect when this subselect is using a 'group by' ??
Date: 2004-06-16 08:42:10
Message-ID: 200406161042.10259.ftm.van.vugt@foxi.nl (view raw or flat)
Thread:
Lists: pgsql-performance
> We don't attempt to make every possible inference (and I don't think
> you'd like it if we did).

I wasn't really asking you to, either ;))

Just trying to achieve a more in-depth understanding of the way things work.

> This example doesn't
> persuade me that it would be worth expending the cycles to do so.

In the real thing I can easily get good processing times by adding an extra 
join with article inside in the group by and simply use the constraint on 
that as well, so I'm ok with any choice you make on this.

I thought this might have been some kind of special case though, given its 
occurence on the use of group by.

> for example, zero and minus zero in IEEE-standard float arithmetic.

Good example, brings back a few memories as well ;)




Thanks for your explanation, Tom!



-- 
Best,




Frank.


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