Bug fix. Fix race condition with parallel MERGE

Author: za-arthur

src/merge.c

@@ -352,15 +352,10 @@ merge_files(void *arg)
 	merge_files_arg *argument = (merge_files_arg *) arg;
 	pgBackup   *to_backup = argument->to_backup;
 	pgBackup   *from_backup = argument->from_backup;
-	char		tmp_file_path[MAXPGPATH];
 	int			i,
 				num_files = parray_num(argument->files);
 	int			to_root_len = strlen(argument->to_root);
 
-	if (to_backup->compress_alg == PGLZ_COMPRESS ||
-		to_backup->compress_alg == ZLIB_COMPRESS)
-		join_path_components(tmp_file_path, argument->to_root, "tmp");
-
 	for (i = 0; i < num_files; i++)
 	{
 		pgFile	   *file = (pgFile *) parray_get(argument->files, i);
@@ -433,8 +428,11 @@ merge_files(void *arg)
 			if (to_backup->compress_alg == PGLZ_COMPRESS ||
 				to_backup->compress_alg == ZLIB_COMPRESS)
 			{
+				char		tmp_file_path[MAXPGPATH];
 				char	   *prev_path;
 
+				join_path_components(tmp_file_path, to_path_tmp, "_tmp");
+
 				/* Start the magic */
 
 				/*

tests/helpers/ptrack_helpers.py

@@ -616,15 +616,16 @@ def backup_node(
         return self.run_pb(cmd_list + options, async, gdb)
 
     def merge_backup(
-            self, backup_dir, instance, backup_id, async=False, gdb=False):
+            self, backup_dir, instance, backup_id, async=False,
+            gdb=False, options=[]):
         cmd_list = [
             "merge",
             "-B", backup_dir,
             "--instance={0}".format(instance),
             "-i", backup_id
         ]
 
-        return self.run_pb(cmd_list, async, gdb)
+        return self.run_pb(cmd_list + options, async, gdb)
 
     def restore_node(
             self, backup_dir, instance, node=False,

tests/merge.py

@@ -69,7 +69,8 @@ def test_merge_full_page(self):
         self.assertEqual(show_backup["backup-mode"], "PAGE")
 
         # Merge all backups
-        self.merge_backup(backup_dir, "node", page_id)
+        self.merge_backup(backup_dir, "node", page_id,
+                          options=["-j", "4"])
         show_backups = self.show_pb(backup_dir, "node")
 
         # sanity check