Re: What's the XID?

Jeff Frost <jeff(at)frostconsultingllc(dot)com> writes:
> On Thu, 27 Dec 2007, Tom Lane wrote:
>> But note that as of 8.3, SELECT-only transactions won't acquire an
>> XID and hence won't advance the counter. So if you're thinking of
>> writing code that depends on that behavior, don't.

> So, the new XID counter won't advance unless there's at least one
> INSERT/UPDATE/DELETE in the transaction? Does it also update for SELECTs that
> call a function which does some write activity?

Any "write" activity causes an XID to be acquired.

> Is there a new counter (or old one that I don't know about) that keeps track
> of the SELECT-only transactions?

There's no global counter. There's a backend-local "virtual transaction
id" counter.

regards, tom lane