Re: Replication/cloning: rsync vs modification dates?

On Tue, Jul 17, 2012 at 07:42:38AM +1000, Chris Angelico wrote:
> On Tue, Jul 17, 2012 at 4:35 AM, Sergey Konoplev
> <sergey.konoplev@postgresql-consulting.com> wrote:
> > On Mon, Jul 16, 2012 at 8:01 PM, Chris Angelico <rosuav@gmail.com> wrote:
> >> On Tue, Jul 17, 2012 at 1:58 AM, Michael Nolan <htfoot@gmail.com> wrote:
> >>> As I understand the docs for rsync, it will use both mod time and file size
> >>> if told not to do checksums.
> >
> > I wonder if it is correct in general to use mtime and size to perform
> > these checks from the point of view of PostgreSQL.
> >
> > If it works with the current version then is there a guaranty that it
> > will work with the future versions?
>
> That was my exact question. Ideally, I'd like to hear from someone who
> works with the Postgres internals, but the question may not even be
> possible to answer.

You might want to look at the hackers list thread I started about the
same topic a week before your post:

    http://archives.postgresql.org/pgsql-hackers/2012-07/msg00416.php

Basically, you can only use mtime/size if you are replaying WAL.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +