Re: ParallelFinish-hook of FDW/CSP (Re: Steps inside ExecEndGather)

2017-02-25 1:40 GMT+09:00 Claudio Freire <klaussfreire@gmail.com>:
> On Fri, Feb 24, 2017 at 1:24 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> On Fri, Feb 24, 2017 at 7:29 PM, Kohei KaiGai <kaigai@kaigai.gr.jp> wrote:
>>> This attached patch re-designed the previous v2 according to Robert's comment.
>>> All I had to do is putting entrypoint for ForeignScan/CustomScan at
>>> ExecShutdownNode,
>>> because it is already modified to call child node first, earlier than
>>> ExecShutdownGather
>>> which releases DSM segment.
>>
>> Aside from the documentation, which needs some work, this looks fine
>> to me on a quick read.
>
> LGTM too.
>
> You may want to clarify in the docs when the hook is called in
> relation to other hooks too.
>
I tried to add a description how custom-scan callbacks performs under the
executor, and when invoked roughly.
However, it is fundamentally not easy for most of people because it assumes
FDW/CSP author understand the overall behavior of optimizer / executor, not
only APIs specifications.

Thanks,
-- 
KaiGai Kohei <kaigai@kaigai.gr.jp>