Improve compatibility between different versions of binary and instance

Author: gsmolk

src/configure.c

@@ -571,7 +571,14 @@ readInstanceConfigFile(const char *instance_name)
 	if (compress_alg)
 		instance->compress_alg = parse_compress_alg(compress_alg);
 
+#if PG_VERSION_NUM >= 110000
+	/* If for some reason xlog-seg-size is missing, then set it to 16MB */
+	if (!instance->xlog_seg_size)
+		instance->xlog_seg_size = DEFAULT_XLOG_SEG_SIZE;
+#endif
+
 	return instance;
+
 }
 
 static void

src/pg_probackup.c

@@ -564,10 +564,18 @@ main(int argc, char *argv[])
 #if PG_VERSION_NUM >= 110000
 	/* Check xlog-seg-size option */
 	if (instance_name &&
-		backup_subcmd != INIT_CMD && backup_subcmd != SHOW_CMD &&
+		backup_subcmd != INIT_CMD &&
 		backup_subcmd != ADD_INSTANCE_CMD && backup_subcmd != SET_CONFIG_CMD &&
 		!IsValidWalSegSize(instance_config.xlog_seg_size))
-		elog(ERROR, "Invalid WAL segment size %u", instance_config.xlog_seg_size);
+	{
+		/* If we are working with instance of PG<11 using PG11 binary,
+		 * then xlog_seg_size is equal to zero. Manually set it to 16MB.
+		 */
+		if (instance_config.xlog_seg_size == 0)
+			instance_config.xlog_seg_size = DEFAULT_XLOG_SEG_SIZE;
+		else
+			elog(ERROR, "Invalid WAL segment size %u", instance_config.xlog_seg_size);
+	}
 #endif
 
 	/* Sanity check of --backup-id option */

src/show.c

@@ -78,7 +78,11 @@ do_show(const char *instance_name, time_t requested_backup_id, bool show_archive
 {
 	if (instance_name == NULL &&
 		requested_backup_id != INVALID_BACKUP_ID)
-		elog(ERROR, "You must specify --instance to use --backup_id option");
+		elog(ERROR, "You must specify --instance to use (-i, --backup-id) option");
+
+	if (show_archive &&
+		requested_backup_id != INVALID_BACKUP_ID)
+		elog(ERROR, "You cannot specify --archive and (-i, --backup-id) options together");
 
 	/*
 	 * if instance_name is not specified,
@@ -105,7 +109,7 @@ do_show(const char *instance_name, time_t requested_backup_id, bool show_archive
 
 		return 0;
 	}
-	/* always use  */
+	/* always use */
 	else if (show_format == SHOW_JSON ||
 			 requested_backup_id == INVALID_BACKUP_ID)
 	{