Update patch.

Changes:
  * set 'on' full_page_writes by user (in document)
  * read "FROM: XX" in backup_label (in xlog.c)
  * check status when pg_stop_backup is executed (in xlog.c)

> Hi, Created a patch in response to comments.
> 
> 
> * Procedure
> 1. Call pg_start_backup('x') on hot standby.
> 2. Take a backup of the data dir.
> 3. Copy the control file on hot standby to the backup.
> 4. Call pg_stop_backup() on hot standby.
> 
> 
> * Behavior
> (take backup)
>  If we execute pg_start_backup() on hot standby then execute restartpoint,
>  write a strings as "FROM: slave" in backup_label and change backup mode,
>  but do not change full_page_writes into "on" forcibly.
> 
>  If we execute pg_stop_backup() on hot standby then rename backup_label
>  and change backup mode, but neither write backup end record and history
>  file nor wait to complete the WAL archiving.
>  pg_stop_backup() is returned this MinRecoveryPoint as result.
> 
>  If we execute pg_stop_backup() on the server promoted then error
>  message is output since read the backup_label.
> 
> (recovery)
>  If we recover with the backup taken on hot standby, MinRecoveryPoint in
>  the control file copied by 3 of above-procedure is used instead of backup
>  end record.
> 
>  If recovery starts as first, BackupEndPoint in the control file is written
>  a same value as MinRecoveryPoint. This is for remembering the value of
>  MinRecoveryPoint during recovery.
> 
>  HINT message("If this has ...") is always output when we recover with the
>  backup taken on hot standby.
> 
> 
> * Problem
>  full_page_writes's problem.
>   > This has the following two problems.
>   >  * pg_start_backup() must set 'on' to full_page_writes of the master that 
>   >    is actual writing of the WAL, but not the standby.
>   >  * The standby doesn't need to connect to the master that's actual 
> writing 
>   >    WAL.
>   >    (Ex. Standby2 in Cascade Replication: Master - Standby1 - Standby2)
>   > 
>   > I'm worried how I should clear these problems.
> 
>  Status: Considering
>   (Latest: http://archives.postgresql.org/pgsql-hackers/2011-08/msg00880.php)
> 
> 
> Regards.
> 
> 
> --------------------------------------------
> Jun Ishizuka
> NTT Software Corporation
> TEL:045-317-7018
> E-Mail: ishizuka....@po.ntts.co.jp
> --------------------------------------------


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

Attachment: standby_online_backup_07.patch
Description: Binary data

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