Re: What's the XID? - Mailing list pgsql-admin

From Tom Lane
Subject Re: What's the XID?
Date
Msg-id 17845.1198778124@sss.pgh.pa.us
Whole thread Raw
In response to Re: What's the XID?  (Jeff Frost <jeff@frostconsultingllc.com>)
Responses Re: What's the XID?  (Jeff Frost <jeff@frostconsultingllc.com>)
List pgsql-admin
Jeff Frost <jeff@frostconsultingllc.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

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