On Mon, Jan 9, 2017 at 12:56 PM, Antonin Houska <a...@cybertec.at> wrote:
> Attached is a draft patch that lets partial aggregation happen at base
> relation level. If the relations contain relatively small number of groups,
> the number of input rows of the aggregation at the query level can be reduced
> this way.  Also, if append relation and postgres_fdw planning is enhanced
> accordingly, patch like this can let us aggregate individual tables on remote
> servers (e.g. shard nodes) and thus reduce the amount of rows subject to the
> final aggregation.

Very interesting.  I don't have time to study this in detail right
now, but as a concept it seems worthwhile.  I think the trick is
figuring out at which levels of the path tree it makes sense to
consider partial aggregation.

Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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