Re: Online base backup from the hot-standby

> > > ERROR: full_page_writes on master is set invalid at least once since
> > > latest checkpoint
> > >
> > > I think this error should be rewritten as
> > > ERROR: full_page_writes on master has been off at some point since
> > > latest checkpoint
> > >
> > > We should be using 'off' instead of 'invalid' since that is what is what
> > > the user sets it to.
> >
> > Sure.
> 
> What about the following message? It sounds more precise to me.
> 
> ERROR: WAL generated with full_page_writes=off was replayed since last
> restartpoint

Okay, I changes the patch to this messages.
If someone says there is a idea better than it, I will consider again.


> > I updated to patch corresponded above-comments.
> 
> Thanks for updating the patch! Here are the comments:
> 
>  	 * don't yet have the insert lock, forcePageWrites could change under us,
>  	 * but we'll recheck it once we have the lock.
>  	 */
> -	doPageWrites = fullPageWrites || Insert->forcePageWrites;
> +	doPageWrites = Insert->fullPageWrites || Insert->forcePageWrites;
> 
> The source comment needs to be modified.
>
>  	 * just turned off, we could recompute the record without full pages, but
>  	 * we choose not to bother.)
>  	 */
> -	if (Insert->forcePageWrites && !doPageWrites)
> +	if ((Insert->fullPageWrites || Insert->forcePageWrites) && !doPageWrites)
> 
> Same as above.

Sure.


> XLogReportParameters() should skip writing WAL if full_page_writes has not been
> changed by SIGHUP.
> 
> XLogReportParameters() should skip updating pg_control if any parameter related
> to hot standby has not been changed.

YES.


> In checkpoint, XLogReportParameters() is called only when wal_level is
> hot_standby.
> OTOH, in walwriter, it's always called even when wal_level is not hot_standby.
> Can't we skip calling XLogReportParameters() whenever wal_level is not
> hot_standby?

Yes, It is possible.


> In do_pg_start_backup() and do_pg_stop_backup(), the spinlock must be held to
> see XLogCtl->lastFpwDisabledLSN.

Yes.


> What about changing the error message to:
> ERROR: WAL generated with full_page_writes=off was replayed during online backup

Okay, too.


--------------------------------------------
Jun Ishizuka
NTT Software Corporation
TEL：045-317-7018
E-Mail: ishizuka.jun@po.ntts.co.jp
--------------------------------------------