Explain EXPLAIN SYNTAX (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 3)
     Identifier k1
     Identifier k2
     Identifier payload
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier f
    Function equals (children 1)
     ExpressionList (children 2)
      Function dictGet (children 1)
       ExpressionList (children 3)
        Literal \'dict_prices_ck_sparse_hashed\'
        Literal \'tag\'
        Function tuple (children 1)
         ExpressionList (children 2)
          Identifier k1
          Identifier k2
      Literal \'pro\'
    ExpressionList (children 3)
     OrderByElement (children 1)
      Identifier k1
     OrderByElement (children 1)
      Identifier k2
     OrderByElement (children 1)
      Identifier payload
