Re: [PATCH] Negative Transition Aggregate Functions (WIP) - Mailing list pgsql-hackers

From David Rowley
Subject Re: [PATCH] Negative Transition Aggregate Functions (WIP)
Date
Msg-id CAApHDvptNWO6VNdzpE7C1GVEmAUcxt0o=w+jr21CrUbjHKk8Pg@mail.gmail.com
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In response to Re: [PATCH] Negative Transition Aggregate Functions (WIP)  (Josh Berkus <josh@agliodbs.com>)
Responses Re: [PATCH] Negative Transition Aggregate Functions (WIP)
List pgsql-hackers
On Sun, Dec 15, 2013 at 2:27 PM, Josh Berkus <josh@agliodbs.com> wrote:
If we're going to disqualify NUMERIC too, we might as well bounce the
feature.  Without a fast FLOAT or NUMERIC, you've lost most of the
target audience.


I don't agree with this. I'm going with the opinion that the more types and aggregates we can support (properly) the better. I'd rather delay implementations of the ones which could change results than see them as a roadblock for the ones we can implement today without this danger.

I think the feature is worth it alone if we could improve COUNT(*). 
It's a bit silly to have to loop through all the tuples in a tuplestore to see how many there are after removing one, when we already knew the count before removing it.  Something like, 10 - 1 .... ummm I dunno, let's count again.. 1, 2, 3, 4, 5, 6, 7, 8, 9.... It's 9!! Where with this patch it's just 10 - 1 *result*. Feels a bit like asking a kid, if you have 10 beans and you take 1 away, how many will there be. You and I know 9, but the kid might have to count them again. PostgreSQL counts them again.

Regards

David Rowley 

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com

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