Re: query cancel issues in contrib/dblink

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Itagaki Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
Cc: pgsql-hackers(at)postgresql(dot)org, Merlin Moncure <mmoncure(at)gmail(dot)com>
Subject: Re: query cancel issues in contrib/dblink
Date: 2010-02-24 19:33:37
Message-ID: 201002241933.o1OJXbP09970@momjian.us
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What happened to this patch?

---------------------------------------------------------------------------

Itagaki Takahiro wrote:
>
> Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
>
> > Takahiro<itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> wrote:
> > > contrib/dblink seems to have no treatments for query cancels.
> > > (1) Users need to wait for completion of remote query.
> > > (2) PGresult objects will be memory leak.
>
> Here is a patch to fix the issues. I hope the fixes will be ported
> to older versions if possible.
>
> (1) is fixed by using non-blocking APIs in libpq. I think we should
> always use non-blocking APIs even if the dblink function itself is
> a blocking-function.
>
> (2) is fixed by RegisterXactCallback(AtEOXact_dblink). However, there
> might be any better solutions -- for example, ResourceOwner framework.
>
>
> > > For (1), asynchronous libpq functions should be used instead of blocking
> > > ones, and wait for the remote query using a loop with CHECK_FOR_INTERRUPTS().
> >
> > How would you structure this loop exactly?
>
> Please check execute_query() and wait_for_result() in the patch.
>
> Regards,
> ---
> ITAGAKI Takahiro
> NTT Open Source Software Center
>

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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
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