Re: [HACKERS] [POC] Faster processing at Gather node

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От Robert Haas
Тема Re: [HACKERS] [POC] Faster processing at Gather node
Дата
Msg-id CA+TgmoYg+J+uKudgP3ZM0w5ycwLUJQ-kh3eouu4qCQXwS5-q_g@mail.gmail.com
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Ответ на Re: [HACKERS] [POC] Faster processing at Gather node  (Amit Kapila <amit.kapila16@gmail.com>)
Ответы Re: [HACKERS] [POC] Faster processing at Gather node
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On Thu, Nov 9, 2017 at 12:08 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> This change looks suspicious to me.  I think here we can't use the
> tupDesc constructed from targetlist.  One problem, I could see is that
> the check for hasOid setting in tlist_matches_tupdesc won't give the
> correct answer.   In case of the scan, we use the tuple descriptor
> stored in relation descriptor which will allow us to take the right
> decision in tlist_matches_tupdesc.  If you try the statement CREATE
> TABLE as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r'; in
> force_parallel_mode=regress, then you can reproduce the problem I am
> trying to highlight.

I tried this, but nothing seemed to be obviously broken.  Then I
realized that the CREATE TABLE command wasn't using parallelism, so I
retried with parallel_setup_cost = 0, parallel_tuple_cost = 0, and
min_parallel_table_scan_size = 0.  That got it to use parallel query,
but I still don't see anything broken.  Can you clarify further?

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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