MDEV-13898 Corruption during online table-rebuilding ALTER of ROW_FORMAT=REDUNDANT tables

This bug is a regression caused by the code refactoring in
commit f5a833c3. It was not present
in any release of the MariaDB server. The bug affects table-rebuilding
ALTER TABLE when the source table is in ROW_FORMAT=REDUNDANT and
contains no virtual columns.

row_log_table_low_redundant(): Log virtual column data only if
virtual columns are present.

mysql-test/suite/innodb/r/innodb-table-online.result

@@ -167,7 +167,8 @@ ROLLBACK;
 connection con1;
 KILL QUERY @id;
 ERROR 70100: Query execution was interrupted
-SET DEBUG_SYNC = 'row_log_table_apply1_before SIGNAL rebuilt WAIT_FOR kill_done';
+SET DEBUG_SYNC = 'row_log_table_apply1_before SIGNAL rebuilt WAIT_FOR dml_done';
+SET DEBUG_SYNC = 'row_log_table_apply2_before SIGNAL applied WAIT_FOR kill_done';
 ALTER TABLE t1 ROW_FORMAT=REDUNDANT;
 # session default
 connection default;
@@ -180,6 +181,10 @@ ddl_online_create_index	1
 ddl_pending_alter_table	1
 ddl_sort_file_alter_table	0
 ddl_log_file_alter_table	0
+BEGIN;
+INSERT INTO t1 VALUES(7,4,2);
+ROLLBACK;
+SET DEBUG_SYNC = 'now SIGNAL dml_done WAIT_FOR applied';
 KILL QUERY @id;
 SET DEBUG_SYNC = 'now SIGNAL kill_done';
 # session con1
@@ -227,6 +232,7 @@ t1	CREATE TABLE `t1` (
   `c3` char(255) NOT NULL,
   PRIMARY KEY (`c1`)
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1 ROW_FORMAT=COMPACT
+ALTER TABLE t1 ROW_FORMAT=REDUNDANT;
 SET DEBUG_SYNC = 'row_log_table_apply1_before SIGNAL rebuilt2 WAIT_FOR dml2_done';
 SET lock_wait_timeout = 10;
 ALTER TABLE t1 ROW_FORMAT=COMPACT, ALGORITHM = INPLACE;

mysql-test/suite/innodb/t/innodb-table-online.test

@@ -158,7 +158,8 @@ let $ID= `SELECT @id := CONNECTION_ID()`;
 --error ER_QUERY_INTERRUPTED
 KILL QUERY @id;
 
-SET DEBUG_SYNC = 'row_log_table_apply1_before SIGNAL rebuilt WAIT_FOR kill_done';
+SET DEBUG_SYNC = 'row_log_table_apply1_before SIGNAL rebuilt WAIT_FOR dml_done';
+SET DEBUG_SYNC = 'row_log_table_apply2_before SIGNAL applied WAIT_FOR kill_done';
 --send
 ALTER TABLE t1 ROW_FORMAT=REDUNDANT;
 
@@ -166,6 +167,10 @@ ALTER TABLE t1 ROW_FORMAT=REDUNDANT;
 connection default;
 SET DEBUG_SYNC = 'now WAIT_FOR rebuilt';
 eval $innodb_metrics_select;
+BEGIN;
+INSERT INTO t1 VALUES(7,4,2);
+ROLLBACK;
+SET DEBUG_SYNC = 'now SIGNAL dml_done WAIT_FOR applied';
 let $ignore= `SELECT @id := $ID`;
 KILL QUERY @id;
 SET DEBUG_SYNC = 'now SIGNAL kill_done';
@@ -201,6 +206,7 @@ WHERE variable_name = 'innodb_encryption_n_rowlog_blocks_encrypted');
 --echo # session con1
 connection con1;
 SHOW CREATE TABLE t1;
+ALTER TABLE t1 ROW_FORMAT=REDUNDANT;
 
 # Exceed the configured innodb_online_alter_log_max_size.
 # The actual limit is a multiple of innodb_sort_buf_size,

storage/innobase/row/row0log.cc

@@ -853,7 +853,7 @@ row_log_table_low_redundant(
 
 	size = rec_get_converted_size_temp(
 		index, tuple->fields, tuple->n_fields, &extra_size);
-	ulint v_size = ventry
+	ulint v_size = num_v
 		? rec_get_converted_size_temp_v(index, ventry) : 0;
 
 	mrec_size = ROW_LOG_HEADER_SIZE + size + v_size + (extra_size >= 0x80);
@@ -909,12 +909,10 @@ row_log_table_low_redundant(
 		rec_convert_dtuple_to_temp(
 			b + extra_size, index, tuple->fields, tuple->n_fields);
 		b += size;
-		if (ventry) {
+		ut_ad(!num_v == !v_size);
+		if (num_v) {
                         rec_convert_dtuple_to_temp_v(b, new_index, ventry);
 			b += v_size;
-		}
-
-		if (num_v) {
 			if (o_ventry) {
 				rec_convert_dtuple_to_temp_v(
 					b, new_index, o_ventry);