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Re: Parallel tuplesort (for parallel B-Tree index creation) - Mailing list pgsql-hackers

From Peter Geoghegan
Subject Re: Parallel tuplesort (for parallel B-Tree index creation)
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Msg-id CAM3SWZSxvacUK8o22Jk0ufSUqW-nVPaBYcLnrse_hMHFbYN84g@mail.gmail.com
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In response to Re: Parallel tuplesort (for parallel B-Tree index creation)  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: Parallel tuplesort (for parallel B-Tree index creation)  (Robert Haas <robertmhaas@gmail.com>)
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On Mon, Sep 26, 2016 at 6:58 PM, Robert Haas <robertmhaas@gmail.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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