Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 4)
     Identifier k
     Identifier v
     Identifier d
     Identifier i
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Subquery (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 2)
           ExpressionList (children 4)
            Function tupleElement (alias k) (children 1)
             ExpressionList (children 2)
              Identifier t
              Literal UInt64_1
            Function tupleElement (alias v) (children 1)
             ExpressionList (children 2)
              Identifier t
              Literal UInt64_2
            Function runningDifference (alias d) (children 1)
             ExpressionList (children 1)
              Identifier v
            Function runningDifference (alias i) (children 1)
             ExpressionList (children 1)
              Function cityHash64 (children 1)
               ExpressionList (children 1)
                Function tupleElement (children 1)
                 ExpressionList (children 2)
                  Identifier t
                  Literal UInt64_1
           TablesInSelectQuery (children 1)
            TablesInSelectQueryElement (children 1)
             TableExpression (children 1)
              Subquery (children 1)
               SelectWithUnionQuery (children 1)
                ExpressionList (children 1)
                 SelectQuery (children 1)
                  ExpressionList (children 1)
                   Function arrayJoin (alias t) (children 1)
                    ExpressionList (children 1)
                     Function array (children 1)
                      ExpressionList (children 6)
                       Literal Tuple_(\'a\', UInt64_1)
                       Literal Tuple_(\'a\', UInt64_2)
                       Literal Tuple_(\'a\', UInt64_3)
                       Literal Tuple_(\'b\', UInt64_11)
                       Literal Tuple_(\'b\', UInt64_13)
                       Literal Tuple_(\'b\', UInt64_15)
    Function equals (children 1)
     ExpressionList (children 2)
      Identifier i
      Literal UInt64_0
