| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Cost model for parallel CREATE INDEX |
| Date: | 2017-03-04 08:31:55 |
| Message-ID: | CAH2-Wzk+7Zf3r7oH3RxSxF9LvCjb+fekfnUv8Y6o58-zgGEMQQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Mar 4, 2017 at 12:23 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> I guess that the workMem scaling threshold thing could be
>> min_parallel_index_scan_size, rather than min_parallel_relation_size
>> (which we now call min_parallel_table_scan_size)?
>
> No, it should be based on min_parallel_table_scan_size, because that
> is the size of the parallel heap scan that will be done as input to
> the sort.
I'm talking about the extra thing we do to prevent parallelism from
being used when per-worker workMem is excessively low. That has much
more to do with projected index size than current heap size.
I agree with everything else you've said, I think.
--
Peter Geoghegan
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