| From: | Jan de Visser <jan(at)de-visser(dot)net> |
|---|---|
| To: | pgsql-general(at)postgresql(dot)org |
| Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Ravi Krishna <sravikrishna3(at)gmail(dot)com> |
| Subject: | Re: PG and undo logging |
| Date: | 2015-05-23 21:04:22 |
| Message-ID: | 7899419.M41HPWkotP@wolverine |
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| Lists: | pgsql-general |
On May 23, 2015 01:48:11 PM David G. Johnston wrote:
> On Sat, May 23, 2015 at 1:34 PM, Ravi Krishna <sravikrishna3(at)gmail(dot)com>
>
> wrote:
> > Is it true that PG does not log undo information, only redo. If true,
> > then how does it bring a database back to consistent state during
> > crash recovery. Just curious.
>
> What does "undo" mean?
>
> David J.
Methinks rolling back the changes that transactions which got interrupted by the
crash scribbled onto the data file. It's an Oracleism where not-consolidated data is
kept in undo- and redo datafiles.
While I roughly understand Postgres' MVCC I don't feel qualified to answer Ravi's
question :-)
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