MDEV-25630 Rollback of instant operation adds wrong column to secondary index

Problem:
=======
  InnoDB alter fails before applying instant operation. So rollback
assigns wrong column to the secondary index field. It leads
to the assert failure in the consecutive alter.

Fix:
===
  InnoDB shouldn't do rollback of instant operation when it fails
before applying instant operation.

mysql-test/suite/innodb/r/instant_alter.result

@@ -2854,3 +2854,30 @@ SELECT COUNT(*) FROM t1;
 COUNT(*)
 16
 DROP TABLE t1;
+#
+# MDEV-25630 Rollback of instant operation adds wrong
+# 	column to secondary index
+#
+CREATE TABLE t1 (f1 INT, f2 INT, f3 INT, f4 INT,
+PRIMARY KEY(f1, f4),
+KEY(f2))ENGINE=InnoDB;
+CREATE TABLE t2 (f1 INT, f2 INT, PRIMARY KEY(f1),
+FOREIGN KEY fk (f2) REFERENCES t2(f1)
+)ENGINE=InnoDB;
+ALTER TABLE t1 ADD f5 INT;
+SET FOREIGN_KEY_CHECKS=0;
+ALTER TABLE t1 DROP COLUMN f3, ADD FOREIGN KEY fk (f1)
+REFERENCES x(x);
+ERROR HY000: Failed to add the foreign key constraint 'test/fk' to system tables
+ALTER TABLE t1 DROP COLUMN f5;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) NOT NULL,
+  `f2` int(11) DEFAULT NULL,
+  `f3` int(11) DEFAULT NULL,
+  `f4` int(11) NOT NULL,
+  PRIMARY KEY (`f1`,`f4`),
+  KEY `f2` (`f2`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+DROP TABLE t1, t2;

mysql-test/suite/innodb/t/instant_alter.test

@@ -917,3 +917,23 @@ INSERT INTO t1(a, b) SELECT '', '' FROM seq_1_to_16;
 SELECT COUNT(*) FROM t1;
 # Cleanup
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-25630 Rollback of instant operation adds wrong
+--echo # 	column to secondary index
+--echo #
+CREATE TABLE t1 (f1 INT, f2 INT, f3 INT, f4 INT,
+		 PRIMARY KEY(f1, f4),
+		 KEY(f2))ENGINE=InnoDB;
+CREATE TABLE t2 (f1 INT, f2 INT, PRIMARY KEY(f1),
+		 FOREIGN KEY fk (f2) REFERENCES t2(f1)
+		)ENGINE=InnoDB;
+
+ALTER TABLE t1 ADD f5 INT;
+SET FOREIGN_KEY_CHECKS=0;
+--error ER_FK_FAIL_ADD_SYSTEM
+ALTER TABLE t1 DROP COLUMN f3, ADD FOREIGN KEY fk (f1)
+	REFERENCES x(x);
+ALTER TABLE t1 DROP COLUMN f5;
+SHOW CREATE TABLE t1;
+DROP TABLE t1, t2;

storage/innobase/handler/handler0alter.cc

@@ -766,6 +766,13 @@ inline void dict_table_t::rollback_instant(
 	const ulint*	col_map)
 {
 	ut_d(dict_sys.assert_locked());
+
+	if (cols == old_cols) {
+		/* Alter fails before instant operation happens.
+		So there is no need to do rollback instant operation */
+		return;
+	}
+
 	dict_index_t* index = indexes.start;
 	mtr_t mtr;
 	mtr.start();