From: | Chris Browne <cbbrowne(at)acm(dot)org> |
---|---|
To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: the XID question |
Date: | 2011-01-19 18:06:58 |
Message-ID: | 878vyg9399.fsf@cbbrowne.afilias-int.info |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
Kevin(dot)Grittner(at)wicourts(dot)gov ("Kevin Grittner") writes:
> Filip Rembia*kowski<plk(dot)zuber(at)gmail(dot)com> wrote:
>> 2011/1/19 Charles.Hou <givemeegn(at)gmail(dot)com>:
>
>>> " select * from mybook" SQL command also increase the XID ?
>>
>> Yes. Single SELECT is a transaction. Hence, it needs a transaction
>> ID.
>
> No, not in recent versions of PostgreSQL. There's virtual
> transaction ID, too; which is all that's needed unless the
> transaction writes something.
>
> Also, as a fine point, if you use explicit database transactions
> (with BEGIN or START TRANSACTION) then you normally get one XID for
> the entire transaction, unless you use SAVEPOINTs.
Erm, "not *necessarily* in recent versions of PostgreSQL."
A read-only transaction won't consume XIDs, but if you don't expressly
declare it read-only, they're still liable to get eaten...
--
(format nil "~S(at)~S" "cbbrowne" "gmail.com")
http://www3.sympatico.ca/cbbrowne/lisp.html
Parenthesize to avoid ambiguity.
From | Date | Subject | |
---|---|---|---|
Next Message | Andres Freund | 2011-01-19 18:31:51 | Re: the XID question |
Previous Message | Fabrízio de Royes Mello | 2011-01-19 17:27:30 | Re: Running PostgreSQL as fast as possible no matter the consequences |