Re: unclear behavior xmax/xmin - Mailing list pgsql-admin

From Andres Freund
Subject Re: unclear behavior xmax/xmin
Date
Msg-id 20181118203428.6oyyhksg46i5mzsv@alap3.anarazel.de
Whole thread Raw
In response to Re: unclear behavior xmax/xmin  (Mariel Cherkassky <mariel.cherkassky@gmail.com>)
List pgsql-admin
Hi,

(Please don't top quote on this list, we do inline responses here)

On 2018-11-18 22:28:24 +0200, Mariel Cherkassky wrote:
> Just exploring the database and trying to understand the logic behind
> things :)
> So after a rollback why the xmax isnt changed back to 0 ? Seems like it
> should be set again to 0.

Because that'd mean that a rollback would have to re-process every page
that the transaction has touched, which'd be pretty expensive for large
transactions. And we couldn't rely on it being 0, because there's also
the case that the machine crashed.

Greetings,

Andres Freund


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