1--- instant_alter_limit.result	2020-05-26 18:01:27.377946439 +0530
2+++ instant_alter_limit,32k.reject	2020-05-26 19:59:19.743877366 +0530
3@@ -43,5 +43,12 @@
4 FROM information_schema.global_status
5 WHERE variable_name = 'innodb_instant_alter_column';
6 instants
7-502
8+506
9 DROP TABLE t;
10+#
11+# MDEV-21787 Alter table failure tries to access uninitialized column
12+#
13+CREATE TABLE t1(f1 INT PRIMARY KEY, f2 TEXT GENERATED ALWAYS AS (SUBSTR(f4, 1, 400)), f3 VARCHAR(500), f4 TEXT)ENGINE=InnoDB ROW_FORMAT=Compact;
14+ALTER TABLE t1 ADD UNIQUE KEY (f2(9));
15+ALTER TABLE t1 ADD COLUMN f5 TEXT, ALGORITHM=INPLACE;
16+DROP TABLE t1;
17