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Re: Deleted WAL files held open by backends in Linux

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Deleted WAL files held open by backends in Linux
Date: 2009-12-01 19:05:19
Message-ID: 5278.1259694319@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Determining whether it's still the current append target is not so
>> cheap though; it would require examining shared-memory status
>> which means taking a lock on that status (and it's a high-traffic
>> lock already).
 
> I haven't reviewed the internal locking techniques, so this may well
> be a dumb question, but...  Since we only care whether the value is
> equal, and an occasional false report of equality wouldn't hurt
> anything, couldn't we bypass the lock in this particular case?

Perhaps, if you didn't mind sometimes getting a wrong answer.
I guess the cost of that would be pretty small in this particular
usage.

			regards, tom lane

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