On 2015-09-08 19:52, Robert Haas wrote:
On Fri, Sep 4, 2015 at 6:52 PM, Ozgun Erdogan <oz...@citusdata.com> wrote:
For Citus, a second part of the question is as FDW writers. We implemented
cstore_fdw, json_fdw, and mongo_fdw, and these wrappers don't benefit from
even the simple join pushdown that doesn't require Map/Reduce.
The PostgreSQL wiki lists 85 foreign data wrappers, and only 18 of these
have support for joins:
https://wiki.postgresql.org/wiki/Foreign_data_wrappers
What do you mean by "support for joins"? Do you mean that only 18 of
the remote data sources can do joins? If so, why does that matter?
I'd be quite happy if a join pushdown or "distributed shuffle" API had
as many as 18 users - I'd be quite happy if it had one (postgres_fdw).
The fact that not all FDWs can support every operation because of
limitations on the remote side isn't a reason not to support those
operations when the remote side is capable.
Agreed. While I personally don't think FDWs are long term answer for
sharding, I do believe that the infrastructure that is being developed
for FDWs (join/aggregate pushdown) is needed anyway and there are many
common issues that need solving in this area for FDWs, sharding and
parallel query.
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Petr Jelinek http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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