Re: aggregates of aggregates - Mailing list pgsql-general

From Tom Lane
Subject Re: aggregates of aggregates
Date
Msg-id 7162.967435324@sss.pgh.pa.us
Whole thread Raw
In response to aggregates of aggregates  (Tor Roberts <pg@econsci.net>)
List pgsql-general
Tor Roberts <pg@econsci.net> writes:
> Does anyone know of any plans to support aggregates of aggregates in the
> future?

Not directly: it makes no sense in the SQL semantic model.  We do have
plans to support subselect-in-FROM (hopefully in 7.2), which would allow
constructs like

SELECT count(*) FROM (SELECT foo,count(*) FROM bar GROUP BY foo)

The same revisions will also be needed before views that involve
grouping or aggregates will work right in all but the simplest cases.

> My solution was to put the result of the first aggregate function in a
> temp table, then doing the other select statement on the temp table. This
> is not very efficient as the temp table can have up to a million records
> in it.

Sounds like a good workaround for now.

            regards, tom lane

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