Re: "Hot standby"?

On 08/11/2009 02:52 PM, Robert Haas wrote:
> On Tue, Aug 11, 2009 at 2:48 PM, Mark Mielke<mark(at)mark(dot)mielke(dot)cc> wrote:
>
>> I remember this debate from 6 months ago. :-)
>>
>> I prefer not to try and fit square pegs into round holes. Streaming
>> replication sounds like the best description. It may not be the keywords
>> that newbies are looking for, but too bad for them. Calling it something
>> different than what it is, just so that people who don't understand why it
>> is wrong will have something that approximates the right understanding, is
>> not a just cause. :-)
>>
>
> Uhm, I think you are confused.
>
> Hot Standby = Allow read-only queries on a PostgreSQL server during
> archive recovery
> Synchronous (or Streaming) Replication = Allow WAL to be streamed on a
> byte level rather than copied file-by-file
>
> Hot Standby is not any sort of replication.

I don't think I was confused before - but I am confused now. :-)

This patch does not provide streaming replication?

Having the standby allow for read-only queries is a "would be nice" for
me, but it's not very useful. I've been monitoring these threads (and
wishing they were at a level I could participate and contribute on),
because I want the ability to have near real time updates such that the
standby can become live. "Hot standby" to me means "the slave is as
close to up-to-date as possible and can potentially take over at any
time in a near instance." This *implies* some sort of streaming
replication (byte level rather than file-by-file) rather than waiting
for WAL logs to become full and shipped.

If this patch doesn't give me near real time replication, then I am
confused about why I would want it at all. pg_standby already gives the
ability to do replication on a per completed WAL log file basis.

Cheers,
mark

--
Mark Mielke<mark(at)mielke(dot)cc>