Re: postgres_fdw vs. force_parallel_mode on ppc

On Wed, Feb 24, 2016 at 12:59 PM, Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> On Wed, Feb 24, 2016 at 5:48 PM, Thomas Munro
> <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
>> Here is a first pass at that. [...]
>
> On Wed, Feb 24, 2016 at 1:23 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> file_fdw is parallel-safe, ...
>
> And here is a patch to apply on top of the last one, to make file_fdw
> return true. But does it really work correctly under parallelism?

Seems like it. Running the regression tests for file_fdw under
force_parallel_mode=regress, max_parallel_degree>0 passes; you can
verify that's actually doing something by using
force_parallel_mode=on, which will result in some predictable
failures. From a theoretical point of view, there's no reason I can
see why reading a file shouldn't work just as well from a parallel
worker as from the leader. They both have the same view of the
filesystem, and in neither case are we trying to write any data; we're
just trying to read it.

Committed these patches after revising the comment you wrote and
adding documentation.

--
Robert Haas
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