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@gmail.com <mailto:gryzman@gmail.com>>
>
>     On Thu, Jan 21, 2010 at 1:12 PM, John Mitchell
>     <mitchelljj98@gmail.com <mailto: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
>
>
>
>
> --
> John J. Mitchell