Explain EXPLAIN QUERY TREE (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 1)
     Function plus (children 1)
      ExpressionList (children 2)
       Function cityHash64 (children 1)
        ExpressionList (children 1)
         Identifier a
       Literal UInt64_10
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier column_swap_test_test
    Function equals (children 1)
     ExpressionList (children 2)
      Function cityHash64 (children 1)
       ExpressionList (children 1)
        Identifier a
      Literal UInt64_0
    Set