(2018/09/18 23:20), Jinhua Luo wrote:
Sorry, the example is not so proper. I just think even if it's a
simple example, e.g. join two co-located tables, the planner should
work out to push down it. Can you confirm the postgresql could detect
co-located tables on the same foreign server and push down queries on
them? Could you give an actual example or point out the relevant
source code paths for reference?
(Let me clarify the context of this question, if the planner supports
co-located push-down, then it's meaningful for manual sharding via
partitioning to remote tables, where it's mostly necessary to join two
or more co-located parent tables in complex queries. If not, the
postgresql instance on which the parent tables are placed (let's say
it's a coordinator node) would be likely the bottleneck.)
You might want to check partitionwise join functionality as well, which
we have in PG11 [1].
Best regards,
Etsuro Fujita
[1]
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=f49842d1ee31b976c681322f76025d7732e860f3
