| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Kevin Grittner <kgrittn(at)ymail(dot)com> |
| Cc: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Amit Kapila <amit(dot)kapila(at)enterprisedb(dot)com>, Simon Riggs <simon(dot)riggs(at)2ndquadrant(dot)com> |
| Subject: | Re: The Future of Aggregation |
| Date: | 2015-06-09 15:00:10 |
| Message-ID: | 20150609150010.GT133018@postgresql.org |
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| Lists: | pgsql-hackers |
Kevin Grittner wrote:
> David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
> > 5. Dependant Aggregates
>
> > Item 5 makes items 1-4 a bit more complex as with this item
> > there's opportunity for very good performance improvements by
> > allowing aggregates like AVG(x) also perform all the required
> > work to allow SUM(x) and COUNT(x) to be calculated for "free" in
> > a query containing all 3 aggregates.
>
> Not only CPU is saved, but the optimizations for materialized views
> would require the aggregate function's transition state to be saved
> in each row, and the duplicate state information among these
> functions would be a waste of space.
Uh, this also requires serialization and deserialization of non-
finalized transition state, no?
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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