instance method configure_connection

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 999
        def configure_connection
          super
          variables = @config.fetch(:variables, {}).stringify_keys

          # Increase timeout so the server doesn't disconnect us.
          # Set to false in config to skip.
          unless @config[:wait_timeout] == false
            wait_timeout = self.class.type_cast_config_to_integer(@config[:wait_timeout])
            wait_timeout = 2147483 unless wait_timeout.is_a?(Integer)
            variables["wait_timeout"] = wait_timeout
          end

          defaults = [":default", :default].to_set

          # Make MySQL reject illegal values rather than truncating or blanking them, see
          # https://dev.mysql.com/doc/refman/en/sql-mode.html#sqlmode_traditional
          # If the user has provided another value for sql_mode, don't replace it.
          # Set sql_mode to false or :default in variables to skip.
          if variables.key?("sql_mode")
            sql_mode_value = variables.delete("sql_mode")
            unless sql_mode_value == false || defaults.include?(sql_mode_value)
              sql_mode = quote(sql_mode_value)
            end
          elsif !defaults.include?(strict_mode?)
            if strict_mode?
              sql_mode = "CONCAT(@@sql_mode, ',TRADITIONAL')"
            else
              sql_mode = "REPLACE(@@sql_mode, 'STRICT_TRANS_TABLES', '')"
              sql_mode = "REPLACE(#{sql_mode}, 'STRICT_ALL_TABLES', '')"
              sql_mode = "REPLACE(#{sql_mode}, 'TRADITIONAL', '')"
            end
            sql_mode = "CONCAT(#{sql_mode}, ',NO_AUTO_VALUE_ON_ZERO')"
          end
          sql_mode_assignment = "@@SESSION.sql_mode = #{sql_mode}, " if sql_mode

          # NAMES does not have an equals sign, see
          # https://dev.mysql.com/doc/refman/en/set-names.html
          # (trailing comma because variable_assignments will always have content)
          if @config[:encoding]
            encoding = +"NAMES #{@config[:encoding]}"
            encoding << " COLLATE #{@config[:collation]}" if @config[:collation]
            encoding << ", "
          end

          # Gather up all of the SET variables...
          variable_assignments = variables.filter_map do |k, v|
            if defaults.include?(v)
              "@@SESSION.#{k} = DEFAULT" # Sets the value to the global or compile default
            elsif !v.nil?
              "@@SESSION.#{k} = #{quote(v)}"
            end
          end.join(", ")

          # ...and send them all in one query
          intent = QueryIntent.new(
            adapter: self,
            processed_sql: "SET #{encoding} #{sql_mode_assignment} #{variable_assignments}",
            name: "SCHEMA"
          )
          intent.execute!
          intent.finish
        end