Re: BUG #13642: no backup_label file in PG_DATA after pg_stop_backup();

On 09/26/2015 06:30 AM, Jeff Janes wrote:
> On Fri, Sep 25, 2015 at 8:16 PM, <amir(dot)rohan(at)mail(dot)com
> <mailto:amir(dot)rohan(at)mail(dot)com>> wrote:
>

> Doesn't create the `backup_label` described in the docs (I'm assuming
> "cluster directory" means data directory, e.g. $PGDATA):
> http://www.postgresql.org/docs/current/static/continuous-archiving.html
>
>
>
> Is backup_label present in your *backup*? That is where it is needed.
> It is not needed in $PGDATA itself. It is created in $PGDATA simply so
> that a copy of it gets included in your backup.
>
> Cheers,
>
> Jeff

No. Well, there's a backup file in the archive directory that looks like
it might be /it/ but it's not named `backup_label` (it wouldn't, since
multiple backups need to coexist).

As mentioned earlier, in the backup procedure docs:

| pg_start_backup creates a backup label file, called backup_label, in |
the cluster directory with information about your backup, including
| the start time and label string. The file is critical to the
| integrity of the backup, should you need to restore from it.

About 8 paragraphs below (where only the brave have stamina to keep
reading):

| It's also worth noting that the pg_start_backup function makes a file
| named backup_label in the database cluster directory, which is
| removed by pg_stop_backup [Ok, I missed that]. This file will
| of course be archived as a part of your backup dump file <...>

But:
- There's no single "backup dump file" that the file is "part of"
(creating a .tgz isn't part of the workflow described). It's
just a sequence of one or more WAL files.
- It doesn't mentioned that the file gets renamed.

The section previous (on using pg_basebackup not sql commands) talks
about something different called a "backup history file", I guess
a "backup_label" becomes one, one PG knows what xlog the backup ends at.

This isn't great documentation. I'll send a patch to pgsql-docs with
suggested improvements.

Thanks for the help,
Amir