MDEV-13561 Mariabackup is incompatible with retroactively created innodb_undo_tablespaces

- Mariabackup supports starting undo tablespace id which is greater
than 1.

extra/mariabackup/common.h

@@ -27,7 +27,9 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 #include <stdarg.h>
 
 
-# define fil_is_user_tablespace_id(i) ((i) > srv_undo_tablespaces_open)
+/** Determine if (i) is a user tablespace id or not. */
+# define fil_is_user_tablespace_id(i) (i != 0 \
+				       && !srv_is_undo_tablespace(i))
 
 #ifdef _MSC_VER
 #define stat _stati64

extra/mariabackup/xtrabackup.cc

@@ -3079,6 +3079,85 @@ xb_fil_io_init(void)
 	fsp_init();
 }
 
+/** Assign srv_undo_space_id_start variable if there are undo tablespace present.
+Read the TRX_SYS page from ibdata1 file and get the minimum space id from
+the first slot rollback segments of TRX_SYS_PAGE_NO.
+@retval DB_ERROR if file open or page read failed.
+@retval DB_SUCCESS if srv_undo_space_id assigned successfully. */
+static dberr_t xb_assign_undo_space_start()
+{
+	ulint		dirnamelen;
+	char		name[1000];
+	pfs_os_file_t	file;
+	byte*		buf;
+	byte*		page;
+	ibool		ret;
+	dberr_t		error = DB_SUCCESS;
+	ulint		space, page_no;
+
+	if (srv_undo_tablespaces == 0) {
+		return error;
+	}
+
+	srv_normalize_path_for_win(srv_data_home);
+	dirnamelen = strlen(srv_data_home);
+	memcpy(name, srv_data_home, dirnamelen);
+
+	if (dirnamelen && name[dirnamelen - 1] != SRV_PATH_SEPARATOR) {
+		name[dirnamelen++] = SRV_PATH_SEPARATOR;
+	}
+
+	ut_snprintf(name + dirnamelen, strlen(name) + strlen("ibdata1"),
+		 "%s", "ibdata1");
+
+	file = os_file_create(innodb_file_data_key, name, OS_FILE_OPEN,
+			      OS_FILE_NORMAL, OS_DATA_FILE, &ret, 0);
+
+	if (ret == FALSE) {
+		fprintf(stderr, "InnoDB: Error in opening %s\n", name);
+		return DB_ERROR;
+	}
+
+	buf = static_cast<byte*>(ut_malloc(2 * UNIV_PAGE_SIZE));
+	page = static_cast<byte*>(ut_align(buf, UNIV_PAGE_SIZE));
+
+retry:
+	ret = os_file_read(file, page, TRX_SYS_PAGE_NO * UNIV_PAGE_SIZE,
+			   UNIV_PAGE_SIZE);
+
+	if (!ret) {
+		fprintf(stderr, "InnoDB: Reading TRX_SYS page failed.");
+		error = DB_ERROR;
+		goto func_exit;
+	}
+
+	/* TRX_SYS page can't be compressed or encrypted. */
+	if (buf_page_is_corrupted(false, page, 0, NULL)) {
+		goto retry;
+	}
+
+	/* 0th slot always points to system tablespace.
+	1st slot should point to first undotablespace which is minimum. */
+
+	page_no = mach_read_ulint(TRX_SYS + TRX_SYS_RSEGS
+				  + TRX_SYS_RSEG_SLOT_SIZE
+				  + TRX_SYS_RSEG_PAGE_NO + page, MLOG_4BYTES);
+	ut_ad(page_no != FIL_NULL);
+
+	space = mach_read_ulint(TRX_SYS + TRX_SYS_RSEGS
+				+ TRX_SYS_RSEG_SLOT_SIZE
+				+ TRX_SYS_RSEG_SPACE + page, MLOG_4BYTES);
+
+	srv_undo_space_id_start = space;
+
+func_exit:
+	ut_free(buf);
+	ret = os_file_close(file);
+	ut_a(ret);
+
+	return error;
+}
+
 /****************************************************************************
 Populates the tablespace memory cache by scanning for and opening data files.
 @returns DB_SUCCESS or error code.*/
@@ -3132,6 +3211,12 @@ xb_load_tablespaces(void)
 
 	/* Add separate undo tablespaces to fil_system */
 
+	err = xb_assign_undo_space_start();
+
+	if (err != DB_SUCCESS) {
+		return err;
+	}
+
 	err = srv_undo_tablespaces_init(FALSE,
 					TRUE,
 					srv_undo_tablespaces,

mysql-test/suite/mariabackup/undo_space_id.opt

+--debug=d,innodb_undo_upgrade
+--innodb_undo_tablespaces=2

mysql-test/suite/mariabackup/undo_space_id.result

+# Create 2 UNDO TABLESPACE(UNDO003, UNDO004)
+CREATE TABLE t1(a varchar(60)) ENGINE INNODB;
+start transaction;
+INSERT INTO t1 VALUES(1);
+# xtrabackup backup
+# Display undo log files from target directory
+undo003
+undo004
+# xtrabackup prepare
+# Display undo log files from targer directory
+undo003
+undo004
+DROP TABLE t1;

mysql-test/suite/mariabackup/undo_space_id.test

+--source include/have_innodb.inc
+--source include/have_debug.inc
+
+--echo # Create 2 UNDO TABLESPACE(UNDO003, UNDO004)
+
+let $basedir=$MYSQLTEST_VARDIR/tmp/backup;
+
+CREATE TABLE t1(a varchar(60)) ENGINE INNODB;
+start transaction;
+INSERT INTO t1 VALUES(1);
+
+--echo # xtrabackup backup
+--disable_result_log
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup --target-dir=$basedir;
+--enable_result_log
+--echo # Display undo log files from target directory
+list_files $basedir undo*;
+
+--echo # xtrabackup prepare
+exec $XTRABACKUP --prepare --apply-log-only --target-dir=$basedir;
+--echo # Display undo log files from targer directory
+list_files $basedir undo*;
+
+DROP TABLE t1;
+rmdir $basedir;

storage/xtradb/srv/srv0start.cc

@@ -1505,14 +1505,12 @@ srv_undo_tablespaces_init(
 
 		if (backup_mode) {
 			ut_ad(!create_new_db);
-			/* MDEV-13561 FIXME: Determine srv_undo_space_id_start
-			from the undo001 file. */
-			srv_undo_space_id_start = 1;
-
 			for (i = 0; i < n_undo_tablespaces; i++) {
 				undo_tablespace_ids[i]
 					= i + srv_undo_space_id_start;
 			}
+
+			prev_space_id = srv_undo_space_id_start - 1;
 		}
 	}