On Mon, Jan 9, 2017 at 12:56 PM, Antonin Houska <ah@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
