Re: Parallel query execution - Mailing list pgsql-hackers

From Jeff Janes
Subject Re: Parallel query execution
Date
Msg-id CAMkU=1zU9myesU-z-F+a1MZC22USAirK=gyJuFJ3_HDN+h9BhQ@mail.gmail.com
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In response to Re: Parallel query execution  (Stephen Frost <sfrost@snowman.net>)
List pgsql-hackers
On Wednesday, January 16, 2013, Stephen Frost wrote:
* Bruce Momjian (bruce@momjian.us) 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.

Cheers,

Jeff

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