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

On Thu, Jan 21, 2010 at 1:12 PM, John Mitchell <mitchelljj98@gmail.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