Re: BUG #15638: pg_basebackup with --wal-method=stream incorrectly generates WAL segment created during backup

On 2/19/19 9:08 PM, Andre Piwoni wrote:

> By the way, you can assert this structure, including now explained
> diff in WAL segment taken during backup, for fetch vs stream WAL
> method by creating master and then creating new slave by taking base
> backup using both methods:
>
> pg_basebackup -h new_slave -D /var/lib/pgsql/10/data -v -P -R -U
> replication --wal-method=stream
> pg_basebackup -h new_slave -D /var/lib/pgsql/10/data -v -P -R -U
> replication --wal-method=fetch

I have verified on different versions of PostgreSQL the identity of
conflict segments received from master node and from pg_basebackup
--wal-method=stream. On PG11+ they are binary identical. However on PG10
and lower the segments are binary different. The logical content are the
same while meaningless tails differ.

In case of pg_basebackup --wal-method=fetch the segments are entirely
the same. And this case doesn't produce any problem in archiving.

I think the backup tools as well as custom archive scripts have to take
account of these points.

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--
Regards,
Maksim Milyutin