From: | Claudio Freire <klaussfreire(at)gmail(dot)com> |
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To: | Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> |
Cc: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: ParallelFinish-hook of FDW/CSP (Re: Steps inside ExecEndGather) |
Date: | 2017-02-06 06:36:39 |
Message-ID: | CAGTBQpYb2i64Ze7AH_tRyef09k34u0KUt21xMXyJX8whV2iQUw@mail.gmail.com |
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On Mon, Feb 6, 2017 at 1:42 AM, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:
> I also had thought an idea to have extra space to Instrumentation structure,
> however, it needs to make Instrumentation flexible-length structure according
> to the custom format by CSP/FDW. Likely, it is not a good design.
> As long as extension can retrieve its custom statistics on DSM area required
> by ExecParallelEstimate(), I have no preference on the hook location.
That's what I had in mind: the hook happens there, but the extension
retrieves the information from some extension-specific DSM area, just
as it would on the ParallelFinish hook.
> One thing we may pay attention is, some extension (not mine) may want to
> collect worker's statistics regardless of Instrumentation (in other words,
> even if plan is not under EXPLAIN ANALYZE).
> It is the reason why I didn't put a hook under the ExecParallelRetrieveInstrumentation().
I don't think you should worry about that as long as it's a hypothetical case.
If/when some extension actually needs to do that, the design can be
discussed with a real use case at hand, and not a hypothetical one.
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