On 2014-08-23 17:28:38 +0100, Simon Riggs wrote:
> On 23 August 2014 14:57, Andres Freund <andres@anarazel.de> wrote:
> > On August 23, 2014 3:49:32 PM CEST, Simon Riggs <simon@2ndQuadrant.com> wrote:
> >>On 22 August 2014 19:30, Alvaro Herrera <alvherre@alvh.no-ip.org>
> >>wrote:
> >>
> >>> Implement ALTER TABLE .. SET LOGGED / UNLOGGED
> >>>
>
> >>When moving from unlogged to logged, where do we remove the init fork?
> >>
> >>Couldn't see the keywords fork or init anywhere in the patch, so maybe
> >>its hidden somewhere.
> >
> > A new relfilenode is filled with the data - the old one, including the init fork, gets removed by the normal
mechanicsof rewriting rels.
>
> Why do we do that? Table rewrite takes hours.
There was a long thread about it on -hackers. Doing it without a rewrite
and without loosing transactional semantics is really rather hard. And
having the capability of doing it with a rewrite is better than not
having it at all.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services