Re: Hash grouping, aggregates - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Hash grouping, aggregates
Date
Msg-id 25794.1044978113@sss.pgh.pa.us
Whole thread Raw
In response to Hash grouping, aggregates  (Greg Stark <gsstark@mit.edu>)
Responses Re: Hash grouping, aggregates  (Bruno Wolff III <bruno@wolff.to>)
List pgsql-hackers
Greg Stark <gsstark@mit.edu> writes:
> So one of the items on the TODO list is "Add hash for evaluating GROUP BY
> aggregates (Tom)" 

It's done in CVS tip ... give it a try.

> The neat thing is that hash aggregates would allow grouping on data types that
> have = operators but no useful < operator.

Hm.  Right now I think that would barf on you, because the parser wants
to find the '<' operator to label the grouping column with, even if the
planner later decides not to use it.  It'd take some redesign of the
query data structure (specifically SortClause/GroupClause) to avoid that.
        regards, tom lane


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