Re: [HACKERS] redolog - for discussion

From: Vadim Mikheev <vadim(at)krs(dot)ru>
To: Jan Wieck <jwieck(at)debis(dot)com>
Cc: PostgreSQL HACKERS <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] redolog - for discussion
Date: 1998-12-16 13:35:25
Message-ID: 3677B71D.C67462B3@krs.ru
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

Jan Wieck wrote:
>
> RECOVER DATABASE {ALL | UNTIL 'datetime' | RESET};
>
...
>
> For the others, the backend starts the recovery program
> which reads the redolog files, establishes database
> connections as required and reruns all the commands in
^^^^^^^^^^^^^^^^^^^^^^^^^^
> them. If a required logfile isn't found, it tells the
^^^^^

I foresee problems with using _commands_ logging for
recovery/replication -:((

Let's consider two concurrent updates in READ COMMITTED mode:

update test set x = 2 where y = 1;

and

update test set x = 3 where y = 1;

The result of both committed transaction will be x = 2
if the 1st transaction updated row _after_ 2nd transaction
and x = 3 if the 2nd transaction gets row after 1st one.
Order of updates is not defined by order in which commands
begun and so order in which commands should be rerun
will be unknown...

Comments?

Vadim

In response to

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message Bruce Momjian 1998-12-16 15:15:36 Re: [COMMITTERS] 'pgsql/src/backend/storage/ipc shmem.c'
Previous Message Vadim Mikheev 1998-12-16 13:00:54 MVCC works in serialized mode!