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Re: What's the XID?

From: Jeff Frost <jeff(at)frostconsultingllc(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Andrew Sullivan <ajs(at)crankycanuck(dot)ca>, pgsql-admin(at)postgresql(dot)org
Subject: Re: What's the XID?
Date: 2007-12-27 23:56:58
Message-ID: Pine.LNX.4.64.0712271550440.2757@glacier.frostconsultingllc.com (view raw or flat)
Thread:
Lists: pgsql-admin
On Thu, 27 Dec 2007, Tom Lane wrote:

> 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.
>

That's a drag as I have quite a few clients who graph the xacts/sec with MRTG. 
Most of these clients have read heavy workloads and it would be great to be 
able to graph read vs write xacts, but a drag if you have no visibility into 
the read xacts.


-- 
Jeff Frost, Owner 	<jeff(at)frostconsultingllc(dot)com>
Frost Consulting, LLC 	http://www.frostconsultingllc.com/
Phone: 650-780-7908	FAX: 650-649-1954

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Subject: Re: What's the XID?
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