Aria: test for ER_KEY_BASED_ON_GENERATED_VIRTUAL_COLUMN

Aria supports virtual columns, but does not support indexes
on virtual columns. Let's issue an appropriate error in this case.

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

+create table t1 (a int, b int as (a+1), c int, index(b)) engine=aria;
+ERROR HY000: Key/Index cannot be defined on a virtual generated column

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

+--source include/have_maria.inc
+--error ER_KEY_BASED_ON_GENERATED_VIRTUAL_COLUMN
+create table t1 (a int, b int as (a+1), c int, index(b)) engine=aria;

storage/maria/ha_maria.cc

@@ -522,6 +522,14 @@ static int table2maria(TABLE *table_arg, data_file_type row_type,
     for (j= 0; j < pos->user_defined_key_parts; j++)
     {
       Field *field= pos->key_part[j].field;
+
+      if (!table_arg->field[field->field_index]->stored_in_db())
+      {
+        my_free(*recinfo_out);
+        my_error(ER_KEY_BASED_ON_GENERATED_VIRTUAL_COLUMN, MYF(0));
+        DBUG_RETURN(HA_ERR_UNSUPPORTED);
+      }
+
       type= field->key_type();
       keydef[i].seg[j].flag= pos->key_part[j].key_part_flag;