On 2015/12/11 14:16, Ashutosh Bapat wrote:
On Thu, Dec 10, 2015 at 11:20 PM, Robert Haas <robertmh...@gmail.com
<mailto:robertmh...@gmail.com>> wrote:


    On Tue, Dec 8, 2015 at 6:40 AM, Etsuro Fujita
    <fujita.ets...@lab.ntt.co.jp <mailto:fujita.ets...@lab.ntt.co.jp>>
    wrote:
    > IMO I want to see the EvalPlanQual fix in the first version for 9.6.

    +1.

I think there is still a lot functionality that is offered without
EvalPlanQual fix. As long as we do not push joins when there are
RowMarks involved, implementation of that hook is not required. We won't
be able to push down joins for DMLs and when there are FOR SHARE/UPDATE
clauses in the query. And there are huge number of queries, which will
be benefitted by the push down even without that support. There's
nothing in this patch, which comes in way of implementing the
EvalPlanQual fix. It can be easily added after committing the first
version. On the other hand, getting minimal (it's not really minimal,
it's much more than that) support for postgres_fdw support committed
opens up possibility to work on multiple items (as listed in my mail) in
parallel.

I am not saying that we do not need EvalPlanQual fix in 9.6. But it's
not needed in the first cut. If we get the first cut in first couple of
months of 2016, there's plenty of room for the fix to go in 9.6. It
would be really bad situation if we could not get postgres_fdw join
pushdown supported in 9.6 because EvalPlanQual hook could not be
committed while the rest of the code is ready. EvalPlanQual fix in core
was being discussed since April 2015. It took 8 months to get that
fixed. Hopefully we won't need that long to implement the hook in
postgres_fdw, but that number says something about the complexity of the
feature.

ISTM that further enhancements are of secondary importance. Let's do the EvalPlanQual fix first. I'll add the RecheckForeignScan callback routine to your version of the postgres_fdw patch as soon as possible.

Best regards,
Etsuro Fujita




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