new_column_from_field

# File activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb, line 204
          def new_column_from_field(table_name, field, _definitions)
            field_name = field.fetch("Field")
            type_metadata = fetch_type_metadata(field["Type"], field["Extra"])
            default, default_function = field["Default"], nil

            if type_metadata.type == :datetime && /\ACURRENT_TIMESTAMP(?:\([0-6]?\))?\z/.match?(default)
              default = "#{default} ON UPDATE #{default}" if /on update CURRENT_TIMESTAMP/.match?(field["Extra"])
              default, default_function = nil, default
            elsif type_metadata.extra == "DEFAULT_GENERATED"
              default = +"(#{default})" unless default.start_with?("(")
              default = default.gsub("\\'", "'")
              default, default_function = nil, default
            elsif type_metadata.type == :text && default&.start_with?("'")
              # strip and unescape quotes
              default = default[1...-1].gsub("\\'", "'")
            elsif default&.match?(/\A\d/)
              # Its a number so we can skip the query to check if it is a function
            elsif default && default_type(table_name, field_name) == :function
              default, default_function = nil, default
            end

            MySQL::Column.new(
              field["Field"],
              lookup_cast_type(type_metadata.sql_type),
              default,
              type_metadata,
              field["Null"] == "YES",
              default_function,
              collation: field["Collation"],
              comment: field["Comment"].presence
            )
          end