pg_basebackup creates a corrupt file for pg_stat_tmp and pg_replslot on a backup location

Hi All,

I tried performing pg_basebackup after creating a symbolic link for
pg_replslot, pg_stat_tmp, pg_log and pg_clog in the source directory and
found that on the backup location pg_stat_tmp, pg_repl_slot is a corrupt
file rather than a link or directory whereas pg_clog and pg_log are getting
skipped. As per the documentation of pg_basebackup, symbolic links on any
directories
other than tablespace and xlog should be skipped. But this statement is not
true for pg_replslot and pg_stat_tmp. The reason is as follows:

pg_basebackup is expecting pg_stat_tmp/pg_replslot to be a directory and
irrespective of whether pg_stat_tmp is empty or not, it will always
include it as a empty directory in backup path. Now, in my case i have
created a softlink for pg_stat_tmp/pg_replslot and pg_basebackup is trying
to create a tar format header without changing the filemode as it does in
case of pg_xlog. Also, linkpath is not considered as in case of pg_tblspc.
This is the reason why a regular file is getting created in the backup path
even though i have a symbolic link in the source path but ideally it should
be skipped.

*Solution:* Skip pg_stat_tmp and pg_replslot if they are symbolic link.
Attached is the patch that fix this issue.

With Regards,
Ashutosh Sharma
EnterpriseDB: *http://www.enterprisedb.com <http://www.enterprisedb.com>*