code: func SortedExplainExpressionList(exprs []Expression) []byte {
  	buffer := bytes.NewBufferString("")
  	exprInfos := make([]string, 0, len(exprs))
  	for _, expr := range exprs {
  		exprInfos = append(exprInfos, expr.ExplainInfo())
  	}
  	sort.Strings(exprInfos)
  	for i, info := range exprInfos {
  		buffer.WriteString(info)
  		if i+1 < len(exprInfos) {
  			buffer.WriteString(", ")
  		}
  	}
  	return buffer.Bytes()
  }
docs: // SortedExplainExpressionList generates explain information for a list of expressions in order.
  // In some scenarios, the expr's order may not be stable when executing multiple times.
  // So we add a sort to make its explain result stable.