check_constraints

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 521
      def check_constraints(table_name)
        if supports_check_constraints?
          scope = quoted_scope(table_name)

          sql = <<~SQL
            SELECT cc.constraint_name AS 'name',
                  cc.check_clause AS 'expression'
            FROM information_schema.check_constraints cc
            JOIN information_schema.table_constraints tc
            USING (constraint_schema, constraint_name)
            WHERE tc.table_schema = #{scope[:schema]}
              AND tc.table_name = #{scope[:name]}
              AND cc.constraint_schema = #{scope[:schema]}
          SQL
          sql += " AND cc.table_name = #{scope[:name]}" if mariadb?

          chk_info = internal_exec_query(sql, "SCHEMA")

          chk_info.map do |row|
            options = {
              name: row["name"]
            }
            expression = row["expression"]
            expression = expression[1..-2] if expression.start_with?("(") && expression.end_with?(")")
            expression = strip_whitespace_characters(expression)

            unless mariadb?
              # MySQL returns check constraints expression in an already escaped form.
              # This leads to duplicate escaping later (e.g. when the expression is used in the SchemaDumper).
              expression = expression.gsub("\\'", "'")
            end

            CheckConstraintDefinition.new(table_name, expression, options)
          end
        else
          raise NotImplementedError
        end
      end