Re: Idea for getting rid of VACUUM FREEZE on cold pages

On Fri, Jun 4, 2010 at 10:18 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Jan Wieck <JanWieck(at)Yahoo(dot)com> writes:
>> On 6/2/2010 3:10 PM, Alvaro Herrera wrote:
>>> I'd prefer a setting that would tell the system to freeze all tuples
>>> that fall within a safety range whenever any tuple in the page is frozen
>>> -- weren't you working on a patch to do this?  (was it Jeff Davis?)
>
>> I just see a lot of cost caused by this "safety range". I yet have to
>> see its real value, other than "feel good".
>
> Jan, you don't know what you're talking about.  I have repeatedly had
> cases where being able to look at xmin was critical to understanding
> a bug.  I *will not* hold still for a solution that effectively reduces
> min_freeze_age to zero.

So, we're talking in circles here. I've already proposed a method
that would avoid the need to wipe out the xmins:

http://archives.postgresql.org/pgsql-hackers/2010-05/msg01485.php

And you said that if we were going to do that we might as well just
freeze sooner:

http://archives.postgresql.org/pgsql-hackers/2010-05/msg01548.php

If you don't want to freeze sooner, let's go back to the method
described in the first email.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company