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Re: Parallel query execution

From: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Parallel query execution
Date: 2013-01-17 03:32:28
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Wednesday, January 16, 2013, Stephen Frost wrote:

> * Bruce Momjian (bruce(at)momjian(dot)us <javascript:;>) wrote:
> > I am not sure how a COPY could be easily parallelized, but I supposed it
> > could be done as part of the 1GB segment feature.  People have
> > complained that COPY is CPU-bound, so it might be very interesting to
> > see if we could offload some of that parsing overhead to a child.
> COPY can certainly be CPU bound but before we can parallelize that
> usefully we need to solve the problem around extent locking when trying
> to do multiple COPY's to the same table.

I think that is rather over-stating it.  Even with unindexed untriggered
tables, I can get some benefit from doing hand-rolled parallel COPY before
the extension lock becomes an issue, at least on some machines.  And with
triggered or indexed tables, all the more so.



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