1 files changed, 50 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/column.rb b/activerecord/lib/active_record/connection_adapters/mysql/column.rb
new file mode 100644
index 0000000000..9c45fdd44a
--- /dev/null
+++ b/activerecord/lib/active_record/connection_adapters/mysql/column.rb
@@ -0,0 +1,50 @@
+module ActiveRecord
+  module ConnectionAdapters
+    module MySQL
+      class Column < ConnectionAdapters::Column # :nodoc:
+        delegate :strict, :extra, to: :sql_type_metadata, allow_nil: true
+
+        def initialize(*)
+          super
+          assert_valid_default
+          extract_default
+        end
+
+        def has_default?
+          return false if blob_or_text_column? # MySQL forbids defaults on blob and text columns
+          super
+        end
+
+        def blob_or_text_column?
+          /\A(?:tiny|medium|long)?blob\b/ === sql_type || type == :text
+        end
+
+        def unsigned?
+          /\bunsigned\z/ === sql_type
+        end
+
+        def case_sensitive?
+          collation && collation !~ /_ci\z/
+        end
+
+        def auto_increment?
+          extra == 'auto_increment'
+        end
+
+        private
+
+        def extract_default
+          if blob_or_text_column?
+            @default = null || strict ? nil : ''
+          end
+        end
+
+        def assert_valid_default
+          if blob_or_text_column? && default.present?
+            raise ArgumentError, "#{type} columns cannot have a default value: #{default.inspect}"
+          end
+        end
+      end
+    end
+  end
+end