Re: What locking mechanism is used for database backup and restore and Master-Slave Replication?

On 01/21/10 16:09, John Mitchell wrote:
> So am I to presume that the current stable version of postgres (before
> 8.5) does require extra locking?

There is currently (before 8.5) no official replication mechanism in
PostgreSQL. There are some 3rd party implementations, for which
information can be gathered here:

http://www.postgresql.org/docs/current/interactive/high-availability.html

http://wiki.postgresql.org/wiki/Replication,_Clustering,_and_Connection_Pooling

> 2010/1/21 Grzegorz Jaśkiewicz <gryzman(at)gmail(dot)com <mailto:gryzman(at)gmail(dot)com>>
>
> On Thu, Jan 21, 2010 at 1:12 PM, John Mitchell
> <mitchelljj98(at)gmail(dot)com <mailto:mitchelljj98(at)gmail(dot)com>> wrote:
> > Hi,
> >
> > In reading the documentation it states that the SQL dump backup
> does not
> > block other operations on the database while it is working.
> yes, pg_dump opens serializable transaction thus guarantees data to be
> the exact snapshot (as opposed to the default isolation level, which
> is called 'read commited' not without reason).
> >
> > I presume that while a restore is occurring that no reads or
> updates are
> > allowed against the restored database.
> nope, what restoring does, is just running all the commands in the
> pg_dump (whether it is binary or textual). So as soon as the database
> is created, it is treated just as any connection, thus allows you to
> connect and use it.
>
>
> > What locking mechanism is used for Master-Slave Replication?
>
> master slave that's introduced in what's to be 9.0 (aka 8.5), uses WAL
> shipping. So it doesn't require any extra locking.
>
>
>
> --
> GJ
>
>
>
>
> --
> John J. Mitchell