CreateQuery /t1 (children 3)
 Identifier /t1
 Columns definition (children 1)
  ExpressionList (children 2)
   ColumnDeclaration a (children 1)
    DataType Int64
   ColumnDeclaration b (children 1)
    DataType Int64
 Storage definition (children 3)
  Function MergeTree (children 1)
   ExpressionList
  Identifier a
  Identifier a