Re: lazy vxid locks, v3

On Mon, Aug 1, 2011 at 11:21 AM, Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> On Mon, 2011-08-01 at 08:12 -0400, Robert Haas wrote:
>> > Is the "&& LocalTransactionIdIsValid(lxid)" a guard against calling
>> > VirtualXactLockTableCleanup twice? Can that happen? Or is it just
>> > defensive coding to avoid making an additional assumption?
>>
>> lxid there is just a local variable storing the value that we
>> extracted from fpLocalTransactionId while holding the lock.  I named
>> it that way just as a mnemonic for the type of value that it was, not
>> intending to imply that it was copied from MyProc->lxid.
>
> I know, this is the other purpose of fpLocalTransactionId that I was
> talking about. Is it just a guard against calling
> VirtualXactLockTableCleanup twice?

I guess you could look at that way. It just seemed like the obvious
way to write the code: we do LockRefindAndRelease() only if we have a
fast-path lock that someone else has pushed into the main table.

--
Robert Haas
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