Explain EXPLAIN QUERY TREE (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 2)
     Function substring (alias t1) (children 1)
      ExpressionList (children 3)
       Function reverse (children 1)
        ExpressionList (children 1)
         Identifier b
       Literal UInt64_1
       Literal UInt64_1
     Identifier a (alias t2)
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier column_swap_test_test
    Function equals (children 1)
     ExpressionList (children 2)
      Function substring (children 1)
       ExpressionList (children 3)
        Function reverse (children 1)
         ExpressionList (children 1)
          Identifier b
        Literal UInt64_1
        Literal UInt64_1
      Literal \'c\'
    Set