You have misread the CQL doc given in the link. According to CQL update grammar it's not possible to use UDF. I see UDF only allowed in select clause... Le 10 mars 2016 22:07, "Kim Liu" <k...@edgewaternetworks.com> a écrit :
> Hello - > I am experimenting with User Defined Functions in Cassandra (3.3) and I am > a bit puzzled by a problem I am having when testing them with cqlsh. I > have tried to find the answers online, but have not had any luck so far. > > According to http://cassandra.apache.org/doc/cql3/CQL.html it looks like > a UDF (User Defined Function) should be useable in an update: > UPDATE atable SET col = some_function(?) ...; > > Current test environment: > cassandra@cqlsh:test_space> show version; > [cqlsh 5.0.1 | Cassandra 3.3 | CQL spec 3.4.0 | Native protocol v4] > > > However, using a value from the row in question as an argument to the UDF > does not seem to work. Here is how I am testing: > CREATE KEYSPACE test_space WITH replication = {'class': > 'SimpleStrategy', 'replication_factor': '1'}; > USE test_space; > CREATE TABLE test_table (idx text, data int, PRIMARY KEY( idx )); > INSERT INTO test_table(idx,data) VALUES( 'abc', 1 ); > CREATE FUNCTION max_int( a int, b int ) CALLED ON NULL INPUT RETURNS int > LANGUAGE java AS 'return (a == null || b == null) ? 0 : ( a > b ? a : b);'; > SELECT * FROM test_table; > UPDATE test_table SET data=max_int(3,4) WHERE idx='abc’; ---- This works > SELECT * FROM test_table; > UPDATE test_table SET data=max_int(data,5) WHERE idx='abc’; ---- This > does not work > > Results: > SyntaxException: <ErrorMessage code=2000 [Syntax error in CQL query] > message="line 1:39 no viable alternative at input ',' (UPDATE test_table > SET data=max_int([data],...)"> > > > > So I am wondering if I am missing something here - or if this is just a > problem with testing with cqlsh. If a UDF is not allowed to be passed a > value from the row that is being updated, then what exactly is the use case > for having a UDF in an UPDATE? If all arguments to the UDF have to be > supplied by the client, then the client might as well perform the > function. Using a UDF in an UPDATE would seem to make the most sense only > if the row data could be accessed, since it could be used to bypass the > need for a SELECT by a client to read the values and perform the operation > on them before doing the UPDATE. > > > Thank you, > Kim Liu > > -------- > Kim Liu > Sr. Software Engineer > k...@edgewaternetworks.com > _______ > “Nothing in the world is more dangerous than sincere ignorance and > conscientious stupidity.” -- Martin Luther King Jr. > > > > >
