Virtual/generated column support for MySQL 5.7.5+ and MariaDB 5.2.0+

MySQL generated columns: https://dev.mysql.com/doc/refman/5.7/en/create-table-generated-columns.html
MariaDB virtual columns: https://mariadb.com/kb/en/mariadb/virtual-computed-columns/

Declare virtual columns with `t.virtual name, type: …, as: "expression"`.
Pass `stored: true` to persist the generated value (false by default).

Example:

    create_table :generated_columns do |t|
      t.string  :name
      t.virtual :upper_name, type: :string,  as: "UPPER(name)"
      t.virtual :name_length, type: :integer, as: "LENGTH(name)", stored: true
      t.index :name_length  # May be indexed, too!
    end

Closes #22589

1 files changed, 1 insertions, 6 deletions

diff --git a/activerecord/test/cases/migration/change_table_test.rb b/activerecord/test/cases/migration/change_table_test.rb
index 8a4242cf1d..ec817a579b 100644
--- a/activerecord/test/cases/migration/change_table_test.rb
+++ b/activerecord/test/cases/migration/change_table_test.rb
@@ -101,12 +101,7 @@ module ActiveRecord
 
       def test_primary_key_creates_primary_key_column
         with_change_table do |t|
-          if current_adapter?(:Mysql2Adapter)
-            @connection.expect :add_column, nil, [:delete_me, :id, :primary_key, { first: true, auto_increment: true, limit: 8, primary_key: true }]
-          else
-            @connection.expect :add_column, nil, [:delete_me, :id, :primary_key, primary_key: true, first: true]
-          end
-
+          @connection.expect :add_column, nil, [:delete_me, :id, :primary_key, primary_key: true, first: true]
           t.primary_key :id, first: true
         end
       end