Re: Synchronized snapshots versus multiple databases

Florian Pflug <fgp@phlo.org> writes:
> On Oct21, 2011, at 17:36 , Tom Lane wrote:
>> 3. Remove the optimization that lets GetOldestXmin ignore XIDs outside
>> the current database.  This sounds bad, but OTOH I don't think there's
>> ever been any proof that this optimization is worth much in real-world
>> usage.  We've already had to lobotomize that optimization for walsender
>> processes, anyway.

> Hm, we've told people who wanted cross-database access to tables in the
> past to either

>   * use dblink or

>   * not split their tables over multiple databases in the first place,
>     and to use schemas instead

> If we remove the GetOldestXmin optimization, we're essentially reversing
> course on this. Do we really wanna go there?

Huh?  The behavior of GetOldestXmin is purely a backend-internal matter.
I don't see how it's related to cross-database access --- or at least,
changing this would not represent a significant move towards supporting
that.
        regards, tom lane