Hello everybody,
I am new to Cassandra and I am trying to extract sketches (e.g. bloom
filter) database side from some given data. I came across user defined
types/functions/aggregates and coded some simple implementation. But now
I am stuck, my questions break down to the below:
1. CREATE TYPE bloomfilter_udt (
2. n_as_sample_size int,
3. m_as_number_of_buckets int,
4. p_as_next_prime_above_m bigint,
5. hash_for_string_coefficient_a list <bigint>,
6. hash_for_number_coefficients_a list <bigint>,
7. hash_for_number_coefficients_b list <bigint>,
8. bloom_filter_as_map map<int,int>
9. );
10.
11. CREATE OR REPLACE FUNCTION bloomfilter_udf (
12. state bloomfilter_udt,
13. valuetext,
14. sample_size int
15. )
16. CALLED ON NULL INPUT
17. RETURNS bloomfilter_udt
18. LANGUAGE java AS
19. $$
20. //fill state which is user defined type bloomfilter_udt with some data
21. returnstate;
22. $$
23. ;
24.
25. CREATE OR REPLACE AGGREGATE bloomfilter_uda (
26. text,
27. int
28. )
29. SFUNC bloomfilter_udf
30. STYPE bloomfilter_udt
31. INITCOND {}
Question 1) When I call the aggregate, I would like to pass sample_size
with a sub-query, e.g.
==> "SELECT bloomfilter_uda(name, (SELECT count(*) FROM test_table))
FROM test_table;" <==
Is that possible with Cassandra?
Question 2) When I try to register the bloomfilter_uda, I get the
following error:
==> InvalidRequest: Error from server: code=2200 [Invalid query]
message="Invalid set literal for (dummy) of type bloomfilter_udt" <==
Can I just pass Cassandra data types as a state (map, list, set)?
Question 3) If I assume, all of the above is my bad, how can I access
the props of the state? Like
==> state.n_as_sample_size <==
Is this somehow possible?
I'd appreciate some help/hints.
Thanks
Andreas
