code: func exprHasSetVar(expr expression.Expression) bool {
  	scalaFunc, isScalaFunc := expr.(*expression.ScalarFunction)
  	if !isScalaFunc {
  		return false
  	}
  	if scalaFunc.FuncName.L == ast.SetVar {
  		return true
  	}
  	for _, arg := range scalaFunc.GetArgs() {
  		if exprHasSetVar(arg) {
  			return true
  		}
  	}
  	return false
  }
docs: // exprHasSetVar checks if the expression has SetVar function.