Re: the XID question

On 1月19日, 下午10時39分, Kevin(dot)Gritt(dot)(dot)(dot)(at)wicourts(dot)gov ("Kevin Grittner")
wrote:
> Filip Rembia*kowski<plk(dot)zu(dot)(dot)(dot)(at)gmail(dot)com> wrote:
> > 2011/1/19 Charles.Hou <giveme(dot)(dot)(dot)(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.
>
my postgresql version is 8.1.3
you means the newer version has a virtual transaction ID. and what's
the maxmium of this virtual id, also 4 billion ?
should i also vacuum freeze the virtual id in the new version when it
reached the 4 billion?

> 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.
>
> -Kevin
>
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