From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> |
Cc: | tgl(at)sss(dot)pgh(dot)pa(dot)us, alvherre(at)alvh(dot)no-ip(dot)org, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: obtaining row locking information |
Date: | 2006-03-21 03:28:21 |
Message-ID: | 200603210328.k2L3SLE15531@candle.pha.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Tatsuo, have you developed a new version of this for 8.2?
---------------------------------------------------------------------------
Tatsuo Ishii wrote:
> > Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> writes:
> > > To accomplish this I need to add following function into
> > > storage/ipc/procarray.c. This is similar to BackendPidGetProc() except
> > > that it accepts xid as an argument. Any objection?
> >
> > > if (xid == 0) /* never match dummy PGPROCs */
> > > return NULL;
> >
> > I think this test should be against InvalidTransactionId, not "0", and
> > the comment is wrong (you are suppressing matches against idle PGPROCs).
> >
> > Also note the comment at the top of the function: once you release
> > ProcArrayLock you have no guarantee that the result means anything at
> > all; and unlike ProcSendSignal, you have no reason to think that the
> > target backend can't quit before you get another cycle. It might be
> > better to return the pid directly rather than assuming it'll still be
> > meaningful to indirect through a returned pointer.
>
> Agreed.
>
> > Also, what are you going to do about prepared transactions? They can
> > hold locks but they don't have PIDs. On the whole, I'm not sure this
> > is a good idea at all, because of that.
>
> For prepared transactions, just showing "0" pids are enough, I
> think. Assuming that in practice most transactions are not prepared
> ones, I think the function is not perfect, but is usefull enough for
> most DBAs.
> --
> Tatsuo Ishii
>
--
Bruce Momjian http://candle.pha.pa.us
SRA OSS, Inc. http://www.sraoss.com
+ If your life is a hard drive, Christ can be your backup. +
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