message: align with convention.
diff: @@ -75,7 +75,7 @@ unique_ptr<LogicalOperator> Optimizer::Optimize(unique_ptr<LogicalOperator> plan
  plan = optimizer.Optimize(move(plan));
  context.profiler.EndPhase();
  // next we make sure that multiple occurences of the same aggregation are only computed once
  - context.profiler.StartPhase("common aggregate expressions");
  + context.profiler.StartPhase("common_aggregate_expressions");
  CommonAggregateOptimizer ca_optimizer;
  ca_optimizer.VisitOperator(*plan);
  context.profiler.EndPhase();
  