Re: Sync Rep: First Thoughts on Code

Hi,

On Wed, Dec 24, 2008 at 6:57 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> Yes, OK. So I think it would only work when full_page_writes = on, and
> has been on since last checkpoint. So two changes:
>
> * We just need a boolean that starts at true every checkpoint and gets
> set to false anytime someone resets full_page_writes or archive_command.
> If the flag is set && full_page_writes = on then we skip the checkpoint
> entirely and use the value from the last checkpoint.

Sounds good.

pg_start_backup on the standby (probably you are planning?) also needs
this logic? If so, resetting full_page_writes or archive_command should
generate its xlog.

I have another thought: should we forbid the reset of archive_command
during online backup? Currently we can do. If we don't need to do so,
we also don't need to track the reset of archiving for fast pg_start_backup.

>
> * My "infra" patch also had a modified version of pg_start_backup() that
> allowed you to specify IMMEDIATE checkpoint or not. Reworking that seems
> a waste of time, and I want to listen to everybody else now and change
> pg_start_backup() so it throws an IMMEDIATE CHECKPOINT and leave it
> there.
>
> Can you work on those also?

Umm.. I'm busy. Of course, I will try it if no one raises his or her hand.
But, I'd like to put coding the core of synch rep ahead of this.

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center