Query doesn't filter UDF result as expected

[Keith Wiley <kw...@keithwiley.com>]

Hive is not filtering on the result of a UDF in the way I expect or desire it to.  The example below shows a very small sample table.  The nested query that follows the table dump attempts to filter the results on the basis of a row_number UDF.  The thing to note is that in the query results, 'rn' increments steadily from 1 to 15.  Next, note that the last clause of the query intended to filter the result to only those result rows where 'rn' equals 1.  In other words, I expected the query to only return the first result row.  What am I missing?  Thanks.

hive> set hive.cli.print.header=true;
hive> select * from test;
OK
foo	bar	user	category	value
foo	bar	user1	catA	1
foo	bar	user1	catB	2
foo	bar	user1	catC	3
foo	bar	user2	catA	99
foo	bar	user2	catB	98
foo	bar	user2	catC	97
foo	bar	user3	catA	100
foo	bar	user3	catB	100
foo	bar	user3	catC	100
foo	bar	user3	catA	200
foo	bar	user3	catB	200
foo	bar	user3	catC	200
foo	bar	user3	catA	300
foo	bar	user3	catB	300
foo	bar	user3	catC	300
Time taken: 0.092 seconds
hive> select * from (
    >     select *, row_number(foo) as rn
    >     from (
    >         select foo, bar, user, category, value
    >         from test
    >             where foo = 'foo'
    >     sort by foo ) a
    > sort by rn ) b
    > where rn = 1;
[...MAP_REDUCE...]
OK
foo	bar	user	category	value	rn
foo	bar	user1	catA	1	1
foo	bar	user1	catB	2	2
foo	bar	user1	catC	3	3
foo	bar	user2	catA	99	4
foo	bar	user2	catB	98	5
foo	bar	user2	catC	97	6
foo	bar	user3	catA	100	7
foo	bar	user3	catB	100	8
foo	bar	user3	catC	100	9
foo	bar	user3	catA	200	10
foo	bar	user3	catB	200	11
foo	bar	user3	catC	200	12
foo	bar	user3	catA	300	13
foo	bar	user3	catB	300	14
foo	bar	user3	catC	300	15
Time taken: 87.933 seconds
hive>


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Keith Wiley     kwiley@keithwiley.com     keithwiley.com    music.keithwiley.com

"I do not feel obliged to believe that the same God who has endowed us with
sense, reason, and intellect has intended us to forgo their use."
                                           --  Galileo Galilei
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