Re: Lazy xid assignment V4

Tom Lane wrote:
> "Florian G. Pflug" <fgp(at)phlo(dot)org> writes:
>> Here is an updated patch, following the discussion.
>> The patch can be found at: http://soc.phlo.org/lazyxidassign.v4.patch
>> (I seems I still can't get attachments through to this list)
>
> Applied with revisions --- mostly cosmetic, but there were a couple of
> things that seemed really broken. In particular, I didn't trust at all
> your use of struct assignment to copy VXIDs into and out of PGPROC.
> I believe that the C compiler is entitled to implement struct assignment
> by bytewise memcpy, for instance, and so it wouldn't be atomic. The
> LocalTransactionId can be fetched or stored atomically, but you have to
> write it as an integer assignment to be sure that that's what happens.
Ah, OK - I wasn't aware of that.

> I also fixed sequence.c to not force XID assignment --- it can perfectly
> well use the LocalTransactionId for what it's doing.
Full ack. I must have missed that user for GetTopTransactionId().

Anyway, thanks for fixing these things.

> Also, I didn't add the proposed regression test, as it seems much too
> fragile --- concurrent autovacuum activity would make it fail, for
> instance.
I was aware that they are fragile, but not that they are *that* fragile ;-)
Anyway they have fullfilled their duty during development, so it's only
fair to let them go now...

Thanks to all of you who helped with making this happen!

greetings, Florian Pflug