Re: Lazy xid assignment V3

"Florian G. Pflug" <fgp(at)phlo(dot)org> writes:
> Tom Lane wrote:
>> "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> writes:
>>> Should there be new a log_line_prefix percent code for virtual
>>> transaction ids? Or should we change the meaning of %x to be virtual
>>> transaction id instead of the real one.
>>
>> I think the latter should be sufficient, especially if we also are showing
>> vxid in pg_locks and pg_stat_activity.

> Hm.. Wouldn't that kind of defeat the idea of a log, if you need the
> output of pg_locks to interpret it? Maybe we should just show both
> values for %x? Or just the xid if it's set, and the vid otherwise?

Well, how do you interpret xid in the log today, if not by reference
to those views? The last option seems quite unworkable, especially
for CSV-based logs.

I suppose there's no great harm in providing %v as an additional
prefix format code ...

> BTW, my current patch doesn't show the vid in pg_stat_activity.

Hmm, actually it looks like the join key for that is supposed to be PID,
so maybe we needn't do anything to it.

> Even in the case of a conflict, two transactions still wouldn't be
> running with the same vid. Rather, the second one would block until
> the first exits, because we hold an ExclusiveLock on the vid.

It's definitely sufficient then ...

regards, tom lane