build_change_column_default_definition

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 435
        def build_change_column_default_definition(table_name, column_name, default_or_changes) # :nodoc:
          column = column_for(table_name, column_name)
          return unless column

          default = extract_new_default_value(default_or_changes)
          ChangeColumnDefaultDefinition.new(column, default)
        end