MDEV-17909 Problem by MariaDB Update 10.1.32 -> 10.2.19 (Incorrect information in file: .frm)

use frm_version, not mysql_version when parsing frm

In particular, virtual columns are stored according to
frm_version. And CHECK TABLE will overwrite mysql_version
to the current server version, so it cannot correctly
describe frm format.

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

@@ -16,3 +16,19 @@ select * from vcol_autoinc;
 pk	v3
 1	1
 drop table vcol_autoinc;
+check table t1  for upgrade;
+Table	Op	Msg_type	Msg_text
+test.t1	check	status	OK
+flush tables;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `Date` datetime(6) NOT NULL,
+  `Data` varbinary(2000) NOT NULL,
+  `a` varchar(100) GENERATED ALWAYS AS (column_get(`Data`,1 as char(100) charset latin1)) VIRTUAL,
+  PRIMARY KEY (`Date`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+ PARTITION BY RANGE (to_days(`Date`))
+(PARTITION `p20181029` VALUES LESS THAN (737361) ENGINE = MyISAM,
+ PARTITION `p20181128` VALUES LESS THAN (737391) ENGINE = MyISAM)
+drop table t1;

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

@@ -11,3 +11,18 @@ select * from vcol_autoinc;
 insert vcol_autoinc (pk) values (1);
 select * from vcol_autoinc;
 drop table vcol_autoinc;
+
+#
+# MDEV-17909 Problem by MariaDB Update 10.1.32 -> 10.2.19 (Incorrect information in file: .frm)
+#
+source include/have_partition.inc;
+copy_file std_data/mdev17909#P#p20181029.MYD $datadir/test/t1#P#p20181029.MYD;
+copy_file std_data/mdev17909#P#p20181029.MYI $datadir/test/t1#P#p20181029.MYI;
+copy_file std_data/mdev17909#P#p20181128.MYD $datadir/test/t1#P#p20181128.MYD;
+copy_file std_data/mdev17909#P#p20181128.MYI $datadir/test/t1#P#p20181128.MYI;
+copy_file std_data/mdev17909.frm $datadir/test/t1.frm;
+copy_file std_data/mdev17909.par $datadir/test/t1.par;
+check table t1  for upgrade;
+flush tables;
+show create table t1;
+drop table t1;

sql/table.cc

@@ -1027,7 +1027,7 @@ bool parse_vcol_defs(THD *thd, MEM_ROOT *mem_root, TABLE *table,
   while (pos < end)
   {
     uint type, expr_length;
-    if (table->s->mysql_version >= 100202)
+    if (table->s->frm_version >= FRM_VER_EXPRESSSIONS)
     {
       uint field_nr, name_length;
       /* see pack_expression() for how data is stored */