CODEWITHSUNDEEP
erlangmapreduceriak
Mark
Mark

Reputation: 69920

How to run an Erlang MapReduce function on Riak?

I'm new to Riak and new to Erlang. I have successfully created and run JS MapReduce jobs, now I'm trying to execute the following Reduce function:

http://web.archive.org/web/20130329021000/http://contrib.basho.com/delete_keys.html

What are the steps to execute this reduce function? Specifically,

Thanks

Upvotes: 1

Views: 1320

Answers (1)

Vincenzo Maggio
Vincenzo Maggio

Reputation: 3869

You should write something like:

MapReduceResult result = client.mapReduce("myBucket")
    .addLinkPhase("bucketX", "test", false)
    .addMapPhase(new NamedJSFunction("Riak.mapValuesJson"), false)
    .addReducePhase(new NamedErlangFunction("riak_kv_mapreduce", "reduce_sort"), true)
.execute();

In this case the reduce phase call the function reduce_sort of erlang module riak_kv_mapreduce. In your case you should call 

.addReducePhase(new NamedErlangFunction("reduce_functions", "delete"), true)

(the true at the end is a flag that set if results have to be returned to client - last step - or not -intermediate step -)

The Erlang files should be compiled as .beam before use and added to 'add_paths' parameters in riak.config like 

{add_paths, ["/home/vinz/riak/custom_modules/"]}

where /home/vinz/riak/custom_modules is the directory containing the compiled Erlang modules.

Refer to Basho Java Client readme for further information. I hope this helps!

Upvotes: 4

Related Questions