CreateQuery topk (children 3)
 Identifier topk
 Columns definition (children 1)
  ExpressionList (children 2)
   ColumnDeclaration val1 (children 1)
    DataType String
   ColumnDeclaration val2 (children 1)
    DataType UInt32
 Storage definition (children 3)
  Function MergeTree
  Identifier val1
  Set