Explain EXPLAIN QUERY TREE (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 1)
     Function dictGet (alias val) (children 1)
      ExpressionList (children 3)
       Literal \'dictdb_01376.dict_exists\'
       Literal \'value\'
       Identifier number
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Function numbers (children 1)
        ExpressionList (children 1)
         Literal UInt64_2
    ExpressionList (children 1)
     Identifier val
    Set
