At Thu, 06 Apr 2017 00:59:49 +0200, Pierre Ducroquet <p.psql@pinaraf.info> wrote in <2008148.rxBNyNRHPZ@peanuts2>
> But it all gets messy when we want to create a streaming standby server using
> pg_basebackup. When backuping Pg 9.5, there is no issue, but backuping Pg 9.6
> afterwards will say "directory "/mnt/ssd/postgres" exists but is not empty".
The documentation says as follows.
https://www.postgresql.org/docs/9.6/static/manage-ag-tablespaces.html
| The location must be an existing, empty directory that is owned
| by the PostgreSQL operating system user.
This explicitly prohibits to share one tablespace directory among
multiple servers. The code is just missing the case of multiple
servers with different versions. I think the bug is rather that
Pg9.6 in the case allowed to create the tablespace.
The current naming rule of tablespace directory was introduced as
of 9.0 so that pg_upgrade (or pg_migrator at the time) can
perform in-place migration. It is not intended to share a
directory among multiple instances with different versions.
That being said, an additional trick in the attached file will
work for you.
regards,
--
Kyotaro Horiguchi
NTT Open Source Software Center
--- reproduce-bug-tblspace.sh 2017-04-06 13:49:10.657803383 +0900
+++ reproduce-bug-tblspace.sh.new 2017-04-06 13:48:45.870024586 +0900
@@ -48,3 +48,14 @@echo "************************ SECOND BASEBACKUP ************************"
-echo "Expecting it to fail with 'directory \"/tmp/pg_bug_backup_tblspace/dest_server/tblspc\" exists but is not
empty'"
+
+echo "stashing tablespace directories of the first backup"
+cd ..
+mv tblspc tblspc.tmp
+mkdir tblspc
+cd datas
+$PG2/pg_basebackup -h /tmp -p $PORT2 -D pg2
--tablespace-mapping=/tmp/pg_bug_backup_tblspace/source_server/tblspc=/tmp/pg_bug_backup_tblspace/dest_server/tblspc
+
+echo "merging tablespace directories"
+cd ..
+mv tblspc.tmp/* tblspc/
+rmdir tblspc.tmp