MDEV-31853 Assertion failure in Column_definition::check_vcol_for_key upon adding FK

when validating vcol's (default, check, etc) in ALTER TABLE
vcol_info->flags are modified in place. This means that if ALTER TABLE
fails for any reason we need to restore them to their original values.

(mroonga was freeing the memory on ::reset() but not on ::close())

mysql-test/suite/vcol/r/innodb_virtual_fk.result

@@ -78,5 +78,24 @@ drop table if exists t2, t1;
 Warnings:
 Note	1051	Unknown table 'test.t2'
 #
+# MDEV-31853 Assertion failure in Column_definition::check_vcol_for_key upon adding FK
+#
+create table t (a int, b int, c int generated always as (a), key(b), key(c));
+alter table t add foreign key (a) references t (b) on update set null, algorithm=nocopy;
+ERROR 0A000: ALGORITHM=NOCOPY is not supported. Reason: Adding foreign keys needs foreign_key_checks=OFF. Try ALGORITHM=COPY
+alter table t add foreign key (a) references t (b);
+show create table t;
+Table	Create Table
+t	CREATE TABLE `t` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) DEFAULT NULL,
+  `c` int(11) GENERATED ALWAYS AS (`a`) VIRTUAL,
+  KEY `b` (`b`),
+  KEY `c` (`c`),
+  KEY `a` (`a`),
+  CONSTRAINT `t_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t` (`b`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+drop table t;
+#
 # End of 10.5 tests
 #

mysql-test/suite/vcol/r/vcol_sql_mode_upgrade.result

@@ -73,6 +73,9 @@ t1	CREATE TABLE `t1` (
   `a` char(5) DEFAULT NULL,
   `v` varchar(5) GENERATED ALWAYS AS (`a`) STORED
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+Warnings:
+Warning	1901	Function or expression '`a`' cannot be used in the GENERATED ALWAYS AS clause of `v`
+Warning	1105	Expression depends on the @@sql_mode value PAD_CHAR_TO_FULL_LENGTH
 SELECT * FROM t1;
 a	v
 1	1
@@ -86,6 +89,9 @@ a	v
 1	1
 2	2
 3	3
+Warnings:
+Warning	1901	Function or expression '`a`' cannot be used in the GENERATED ALWAYS AS clause of `v`
+Warning	1105	Expression depends on the @@sql_mode value PAD_CHAR_TO_FULL_LENGTH
 DROP TABLE t1;
 #
 # Fixing a Maria-10.2.26 table with a stored VARCHAR column
@@ -201,6 +207,9 @@ a	v
 1	1
 2	2
 3	3
+Warnings:
+Warning	1901	Function or expression '`a`' cannot be used in the GENERATED ALWAYS AS clause of `v`
+Warning	1105	Expression depends on the @@sql_mode value PAD_CHAR_TO_FULL_LENGTH
 DROP TABLE t1;
 #
 # Fixing a Maria-10.2.26 table with a virtual VARCHAR column

mysql-test/suite/vcol/t/innodb_virtual_fk.test

@@ -100,6 +100,16 @@ create or replace table t2 (id int, id2 int as (id) virtual, check (id2), foreig
 
 drop table if exists t2, t1;
 
+--echo #
+--echo # MDEV-31853 Assertion failure in Column_definition::check_vcol_for_key upon adding FK
+--echo #
+create table t (a int, b int, c int generated always as (a), key(b), key(c));
+--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
+alter table t add foreign key (a) references t (b) on update set null, algorithm=nocopy;
+alter table t add foreign key (a) references t (b);
+show create table t;
+drop table t;
+
 --echo #
 --echo # End of 10.5 tests
 --echo #

sql/sql_alter.cc

@@ -254,6 +254,13 @@ Alter_info::algorithm(const THD *thd) const
 
 uint Alter_info::check_vcol_field(Item_field *item) const
 {
+  /*
+    vcol->flags are modified in-place, so we'll need to reset them
+    if ALTER fails for any reason
+  */
+  if (item->field && !item->field->table->needs_reopen())
+    item->field->table->mark_table_for_reopen();
+
   if (!item->field &&
       ((item->db_name.length && !db.streq(item->db_name)) ||
        (item->table_name.length && !table_name.streq(item->table_name))))

storage/mroonga/ha_mroonga.cpp

@@ -4946,6 +4946,17 @@ int ha_mroonga::wrapper_close()
   MRN_DBUG_ENTER_METHOD();
   MRN_SET_WRAP_SHARE_KEY(share, table->s);
   MRN_SET_WRAP_TABLE_KEY(this, table);
+#ifdef MRN_HANDLER_HAVE_CHECK_IF_SUPPORTED_INPLACE_ALTER
+  if (alter_key_info_buffer) {
+    my_free(alter_key_info_buffer);
+    alter_key_info_buffer = NULL;
+  }
+#else
+  if (wrap_alter_key_info) {
+    my_free(wrap_alter_key_info);
+    wrap_alter_key_info = NULL;
+  }
+#endif
 #ifdef MRN_HANDLER_HAVE_HA_CLOSE
   error = wrap_handler->ha_close();
 #else