On Mon, Jan 28, 2019, at 10:25, Michael Paquier wrote:
> On Mon, Jan 28, 2019 at 09:05:26AM +0100, Magnus Hagander wrote:
> > And for plain format, we'd do the same -- sync after each file segment, and
> > then a final one of the directory when done, right?
>
> Well, the code is doing a double amount of work in its current shape
> as we call fsync_pgdata() for the plain format, which cascades to
> pg_wal and all its files, so it seems to me that there is little point
> in issuing a sync when each segment is finished streaming if that's
> what you mean.
Agreed.
While reading the doc page for the pg_basebackup, I've been confused by the
fact that it says WAL files will be written to .tarballs (either base.tar or
pg_wal.tar) when pg_basebackup is instructed to stream WALs alongside the
backup itself. I think it makes sense to elaborate that it only happens when
tar format is specified (doc patch is attached).
Cheers,
Oleksii
diff --git a/doc/src/sgml/ref/pg_basebackup.sgml
b/doc/src/sgml/ref/pg_basebackup.sgml
index 57dc83b620..c4f3950e5b 100644
--- a/doc/src/sgml/ref/pg_basebackup.sgml
+++ b/doc/src/sgml/ref/pg_basebackup.sgml
@@ -306,8 +306,8 @@ PostgreSQL documentation
backup will fail and be unusable.
</para>
<para>
- The write-ahead log files will be written to
- the <filename>base.tar</filename> file.
+ When tar format mode is used, the write-ahead log files will be
+ written to the <filename>base.tar</filename> file.
</para>
</listitem>
</varlistentry>
@@ -326,9 +326,10 @@ PostgreSQL documentation
requires no extra write-ahead logs to be saved on the master.
</para>
<para>
- The write-ahead log files are written to a separate file
- named <filename>pg_wal.tar</filename> (if the server is a version
- earlier than 10, the file will be named
<filename>pg_xlog.tar</filename>).
+ When tar format mode is used, the write-ahead log files will be
+ written to a separate file named <filename>pg_wal.tar</filename>
+ (if the server is a version earlier than 10, the file will be named
+ <filename>pg_xlog.tar</filename>).
</para>
<para>
This value is the default.
