code: func (b *executorBuilder) buildTrace(v *plannercore.Trace) Executor {
  	return &TraceExec{
  		baseExecutor: newBaseExecutor(b.ctx, v.Schema(), v.ExplainID()),
  		stmtNode:     v.StmtNode,
  		builder:      b,
  		format:       v.Format,
  	}
  }
docs: // buildTrace builds a TraceExec for future executing. This method will be called
  // at build().