Map basebackup tablespaces using a tablespace_map file

Windows can't reliably restore symbolic links from a tar format, so
instead during backup start we create a tablespace_map file, which is
used by the restoring postgres to create the correct links in pg_tblspc.
The backup protocol also now has an option to request this file to be
included in the backup stream, and this is used by pg_basebackup when
operating in tar mode.

This is done on all platforms, not just Windows.

This means that pg_basebackup will not not work in tar mode against 9.4
and older servers, as this protocol option isn't implemented there.

Amit Kapila, reviewed by Dilip Kumar, with a little editing from me.

1 files changed, 11 insertions, 1 deletions

diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 2179bf719e1..329bb8ca25d 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -51,6 +51,7 @@ pg_start_backup(PG_FUNCTION_ARGS)
 	bool		fast = PG_GETARG_BOOL(1);
 	char	   *backupidstr;
 	XLogRecPtr	startpoint;
+	DIR		   *dir;
 
 	backupidstr = text_to_cstring(backupid);
 
@@ -59,7 +60,16 @@ pg_start_backup(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 		   errmsg("must be superuser or replication role to run a backup")));
 
-	startpoint = do_pg_start_backup(backupidstr, fast, NULL, NULL);
+	/* Make sure we can open the directory with tablespaces in it */
+	dir = AllocateDir("pg_tblspc");
+	if (!dir)
+		ereport(ERROR,
+				(errmsg("could not open directory \"%s\": %m", "pg_tblspc")));
+
+	startpoint = do_pg_start_backup(backupidstr, fast, NULL, NULL,
+									dir, NULL, NULL, false, true);
+
+	FreeDir(dir);
 
 	PG_RETURN_LSN(startpoint);
 }