instance method explain

# File activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb, line 27
        def explain(arel_or_sql, binds = [], options = [])
          sql, binds = to_sql_and_binds(arel_or_sql, binds)
          sql = build_explain_clause(options) + " " + sql
          start   = Process.clock_gettime(Process::CLOCK_MONOTONIC)
          result  = select_all(sql, "EXPLAIN", binds)
          elapsed = Process.clock_gettime(Process::CLOCK_MONOTONIC) - start

          MySQL::ExplainPrettyPrinter.new.pp(result, elapsed)
        end