On 2017-04-08 1:50 AM, Michael Banck wrote:
>> - PGFDW: push down aggregates
>
> As the list is getting rather large, I am not sure this one merits
> inclusion, but I don't how much it improves things, really.
I believe this absolutely merits inclusion in the announcement, though not as a
top 3 item.
Pushing down aggregates is huge for the scalability and performance of federated
queries.
If one is for example summarizing a billion remote rows into a dozen rows, this
change means the GROUP BY and aggregation happens remotely and then only a dozen
rows are passed over the wire instead of a billion rows.
Next to pushing down projections or restrictions, the aggregate pushdown means
the difference for a large fraction of common queries to be feasible versus not.
It means that say a billion row aggregate takes effectively zero time of the
client Postgres' resources.
-- Darren Duncan