Re: Libpq COPY optimization

Can I get an updated patch for this?

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Tom Lane wrote:
> "Alon Goldshuv" <agoldshuv(at)greenplum(dot)com> writes:
> > Please help me understand this better. It appears to me that when the
> > client->backend pipe fills up, pqSendSome() consumes any incoming
> > NOTICE/WARNING messages before waiting, which should prevent deadlock.
>
> Hm, I had forgotten that the low-level pqSendSome routine does that.
> That makes the PQconsumeInput call in PQputCopyData redundant (or
> almost; see below). The parseInput call is still needed, because it's
> there to pull NOTICE messages out of the input buffer and get rid of
> them, rather than possibly having the input buffer grow to exceed
> memory. But when there's nothing for it to do, parseInput is cheap
> enough that there's no real need to bypass it.
>
> In short, if you just remove the PQconsumeInput call I think you'll find
> that it does what you want.
>
> The only case where it's helpful to have it there is if there's a
> incomplete message in the input buffer, as parseInput isn't quite so
> fast if it has to determine that the message is incomplete. Without
> the PQconsumeInput call, the incomplete-message state could persist
> for a long time, and you'd pay the parseInput overhead each time through
> PQputCopyData. However, that's certainly not the normal situation,
> so I think we could leave that case slightly pessimal. It's certainly
> true that that path in parseInput is a lot faster than a kernel call,
> so it'd still be better than it is now.
>
> regards, tom lane
>
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