| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: EXPLAIN ANALYZE for parallel query doesn't report the SortMethod information. |
| Date: | 2016-07-07 14:07:24 |
| Message-ID: | 26010.1467900444@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> writes:
> On Thu, Jul 7, 2016 at 1:23 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>> I found $SUBJECT while trying to test parallel queries. Is this a bug?
Presumably the instrumentation data needed for that is not getting
returned from the worker to the leader. I would bet there's a lot
of other plan-node-specific data that doesn't work either.
> I think this can never happen for force_parallel_mode TO off, because
> we don't generate a gather on top of sort node. The reason why we are
> able to push Sort below gather, because it is marked as parallel_safe
> (create_sort_path). I think we should not mark it as parallel_safe.
That seems rather ridiculous. An oversight in managing EXPLAIN data
is not a sufficient reason to cripple parallel query.
regards, tom lane
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