SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 2)
    Function array (alias arr) (children 1)
     ExpressionList
    Function if (children 1)
     ExpressionList (children 3)
      Function empty (children 1)
       ExpressionList (children 1)
        Identifier arr
      Literal UInt64_0
      Function arrayElement (children 1)
       ExpressionList (children 2)
        Identifier arr
        Literal Int64_-1