change_column

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 414
        def change_column(table_name, column_name, type, options = {}) #:nodoc:
          clear_cache!
          quoted_table_name = quote_table_name(table_name)
          quoted_column_name = quote_column_name(column_name)
          sql_type = type_to_sql(type, options)
          sql = "ALTER TABLE #{quoted_table_name} ALTER COLUMN #{quoted_column_name} TYPE #{sql_type}"
          if options[:collation]
            sql << " COLLATE \"#{options[:collation]}\""
          end
          if options[:using]
            sql << " USING #{options[:using]}"
          elsif options[:cast_as]
            cast_as_type = type_to_sql(options[:cast_as], options)
            sql << " USING CAST(#{quoted_column_name} AS #{cast_as_type})"
          end
          execute sql

          change_column_default(table_name, column_name, options[:default]) if options.key?(:default)
          change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
          change_column_comment(table_name, column_name, options[:comment]) if options.key?(:comment)
        end