SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function materialize (alias m) (children 1)
     ExpressionList (children 1)
      Function map (children 1)
       ExpressionList (children 4)
        Literal \'a\'
        Literal UInt64_2
        Literal \'b\'
        Literal NULL
   ExpressionList (children 3)
    Function arrayElement (children 1)
     ExpressionList (children 2)
      Identifier m
      Function materialize (children 1)
       ExpressionList (children 1)
        Function toNullable (children 1)
         ExpressionList (children 1)
          Literal \'a\'
    Function arrayElement (children 1)
     ExpressionList (children 2)
      Identifier m
      Function materialize (children 1)
       ExpressionList (children 1)
        Function toNullable (children 1)
         ExpressionList (children 1)
          Literal \'b\'
    Function arrayElement (children 1)
     ExpressionList (children 2)
      Identifier m
      Function materialize (children 1)
       ExpressionList (children 1)
        Function toNullable (children 1)
         ExpressionList (children 1)
          Literal \'c\'