At Sun, 02 Apr 2017 16:30:24 +0300, Konstantin Knizhnik 
<k.knizh...@postgrespro.ru> wrote in <58e0fcf0.2070...@postgrespro.ru>
> Hi hackers and personally Robet (you are the best expert in both
> areas).
> I want to ask one more question concerning parallel execution and FDW.
> Below are two plans for the same query (TPC-H Q5): one for normal
> tables, another for FDW to vertical representation of the same data.
> FDW supports analyze function and is expected to produce the similar
> statistic as for original tables.
<big explain>
> The plans look very similar, but first one is parallel and second -
> not.
> My FDW provides implementation for IsForeignScanParallelSafe which
> returns true.
> I wonder what can prevent optimizer from using parallel plan in this
> case?

Parallel execution requires partial paths. It's the work for
GetForeignPaths of your FDW.


Kyotaro Horiguchi
NTT Open Source Software Center

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