| From: | Peter Geoghegan <pg(at)heroku(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Corey Huinker <corey(dot)huinker(at)gmail(dot)com> |
| Subject: | Re: Parallel tuplesort (for parallel B-Tree index creation) |
| Date: | 2016-09-26 19:40:05 |
| Message-ID: | CAM3SWZSxvacUK8o22Jk0ufSUqW-nVPaBYcLnrse_hMHFbYN84g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Sep 26, 2016 at 6:58 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> That requires some kind of mutual exclusion mechanism, like an LWLock.
>
> No, it doesn't. Shared memory queues are single-reader, single-writer.
The point is that there is a natural dependency when merging is
performed eagerly within the leader. One thing needs to be in lockstep
with the others. That's all.
--
Peter Geoghegan
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