Re: CLUSTER FREEZE

On Fri, Oct 25, 2013 at 2:12 AM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> On 2013-10-24 17:17:22 -0700, Josh Berkus wrote:
>> On 10/24/2013 04:55 PM, Robert Haas wrote:
>> > On Thu, Oct 24, 2013 at 1:09 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
>> >> On 10/23/2013 09:58 PM, Amit Kapila wrote:
>> >>> I wonder why anyone would like to freeze during CLUSTER command when
>> >>> they already have separate way (VACUUM FREEZE) to achieve it, do you
>> >>> know or can think of any case where user wants to do it along with
>> >>> Cluster command?
>> >>
>> >> "If I'm rewriting the table anyway, let's freeze it".
>> >>
>> >> Otherwise, you have to write the same pages twice, if both CLUSTER and
>> >> FREEZE are required.
>> >
>> > I wonder if we should go so far as to make this the default behavior,
>> > instead of just making it an option.
>>
>> +1 from me. Can you think of a reason you *wouldn't* want to freeze?
>
> It makes content from the future appear when you start using the
> relation in a query/session with an older snapshot. Currently CLUSTER is
> safe against that.

Eh, what? We wouldn't freeze XIDs that don't precede RecentGlobalXmin.

--
Robert Haas
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