Re: [POC] Faster processing at Gather node

On Thu, Nov 9, 2017 at 12:08 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)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
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