MDEV-19630 ALTER TABLE ... ADD COLUMN damages foreign keys

		which are pointed to the table being altered
Problem:
========
	InnoDB failed to change the column name present in foreign key cache
for instant add column. So it leads to column mismatch for the consecutive
rename of column.

Solution:
=========
	Evict the foreign key information from cache and load the foreign
key information again for instant operation.

Author: Thirunarayanan

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

@@ -128,3 +128,29 @@ HANDLER h READ `PRIMARY` PREV WHERE 0;
 pk	f1	f2	f3	f4	f5	f6	f7	f8	filler
 HANDLER h CLOSE;
 DROP TABLE t1;
+CREATE TABLE t1(f1 int not null, primary key(f1))engine=innodb;
+CREATE TABLE t2(f1 INT AUTO_INCREMENT NOT NULL, f2 INT NOT NULL,
+status ENUM ('a', 'b', 'c'), INDEX idx1(f2),
+PRIMARY KEY(f1),
+FOREIGN KEY (f2) REFERENCES t1(f1))ENGINE=InnoDB;
+ALTER TABLE t1 CHANGE f1 f1_id INT NOT NULL, ADD f3 VARCHAR(255) DEFAULT NULL;
+ALTER TABLE t1 CHANGE f1_id f1 INT NOT NULL;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) NOT NULL,
+  `f3` varchar(255) DEFAULT NULL,
+  PRIMARY KEY (`f1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `f1` int(11) NOT NULL AUTO_INCREMENT,
+  `f2` int(11) NOT NULL,
+  `status` enum('a','b','c') DEFAULT NULL,
+  PRIMARY KEY (`f1`),
+  KEY `idx1` (`f2`),
+  CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`f2`) REFERENCES `t1` (`f1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+ALTER TABLE t2 CHANGE status status VARCHAR(20) DEFAULT NULL;
+DROP TABLE t2, t1;

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

@@ -134,5 +134,23 @@ HANDLER h READ `PRIMARY` PREV WHERE 0;
 # Cleanup
 HANDLER h CLOSE;
 DROP TABLE t1;
+
+# MDEV-19630 ALTER TABLE ... ADD COLUMN damages foreign keys which are pointed
+#		to the table being altered
+CREATE TABLE t1(f1 int not null, primary key(f1))engine=innodb;
+CREATE TABLE t2(f1 INT AUTO_INCREMENT NOT NULL, f2 INT NOT NULL,
+		status ENUM ('a', 'b', 'c'), INDEX idx1(f2),
+		PRIMARY KEY(f1),
+		FOREIGN KEY (f2) REFERENCES t1(f1))ENGINE=InnoDB;
+
+ALTER TABLE t1 CHANGE f1 f1_id INT NOT NULL, ADD f3 VARCHAR(255) DEFAULT NULL;
+ALTER TABLE t1 CHANGE f1_id f1 INT NOT NULL;
+
+SHOW CREATE TABLE t1;
+SHOW CREATE TABLE t2;
+
+ALTER TABLE t2 CHANGE status status VARCHAR(20) DEFAULT NULL;
+DROP TABLE t2, t1;
+
 --let $datadir= `select @@datadir`
 --remove_file $datadir/test/load.data

storage/innobase/handler/handler0alter.cc

@@ -7441,14 +7441,14 @@ innobase_drop_foreign_try(
 }
 
 /** Rename a column in the data dictionary tables.
-@param[in] user_table	InnoDB table that was being altered
-@param[in] trx		data dictionary transaction
-@param[in] table_name	Table name in MySQL
-@param[in] nth_col	0-based index of the column
-@param[in] from		old column name
-@param[in] to		new column name
-@param[in] new_clustered whether the table has been rebuilt
-@param[in] is_virtual	whether it is a virtual column
+@param[in] user_table		InnoDB table that was being altered
+@param[in] trx			Data dictionary transaction
+@param[in] table_name		Table name in MySQL
+@param[in] nth_col		0-based index of the column
+@param[in] from			old column name
+@param[in] to			new column name
+@param[in] new_clustered	whether the table has been rebuilt
+@param[in] evict_fk_cache	Evict the fk info from cache
 @retval true Failure
 @retval false Success */
 static MY_ATTRIBUTE((nonnull, warn_unused_result))
@@ -7460,7 +7460,8 @@ innobase_rename_column_try(
 	ulint			nth_col,
 	const char*		from,
 	const char*		to,
-	bool			new_clustered)
+	bool			new_clustered,
+	bool			evict_fk_cache)
 {
 	pars_info_t*	info;
 	dberr_t		error;
@@ -7644,7 +7645,8 @@ innobase_rename_column_try(
 		}
 	}
 
-	if (new_clustered) {
+	/* Reload the foreign key info for instant table too. */
+	if (new_clustered || evict_fk_cache) {
 		std::for_each(fk_evict.begin(), fk_evict.end(),
 			      dict_foreign_remove_from_cache);
 	}
@@ -7699,7 +7701,8 @@ innobase_rename_columns_try(
 					    col_n,
 					    cf->field->field_name.str,
 					    cf->field_name.str,
-					    ctx->need_rebuild())) {
+					    ctx->need_rebuild(),
+					    ctx->is_instant())) {
 					return(true);
 				}
 				goto processed_field;