Re: Functional dependencies and GROUP BY

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Peter Eisentraut <peter_e(at)gmx(dot)net>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Functional dependencies and GROUP BY
Date: 2010-06-08 01:41:24
Message-ID: 20100608014124.GJ21875@tamriel.snowman.net
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* Peter Eisentraut (peter_e(at)gmx(dot)net) wrote:
> This is frequently requested by MySQL converts (and possibly others).

I'd certainly love to see it- but let's not confuse people by implying
that it would actually act the way MySQL does. It wouldn't, because
what MySQL does is alot closer to 'distinct on' and is patently insane
to boot. Again, I'd *love* to see this be done in PG, but when we
document it and tell people about it, *please* don't say it's similar in
any way to MySQL's "oh, we'll just pick a random value from the columns
that aren't group'd on" implementation.

> At this point, this patch could use some review and testing with unusual
> queries that break my implementation. ;-)

I'll give it a shot... :)

Thanks!

Stephen

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