On Wed, Oct 26, 2011 at 2:53 PM, Elias Levy <fearsome.lucid...@gmail.com> wrote:
> For instance:
>
> mr = Riak::MapReduce.new(riak)
> mr.add('bucket', 'key')
> mr.reduce("function(v) { return [] }", :keep => true))
> This returns:
> {"bucket"=>"key"}I believe this one is explainable by a known Riak 1.0 MapReduce bug: https://issues.basho.com/show_bug.cgi?id=1185 If you check your Riak log, I bet you'll see an error message, and if the final run of a reduce fails, then in Riak 1.0.[0,1] the reduce phase sends on its [possibly unreduced] inputs, instead of failing. I hope to fix this soon. > Doing instead: > mr = Riak::MapReduce.new(riak) > mr.add('bucket', 'key') > mr.reduce("riak_kv_mapreduce:reduce_identity", :language => "erlang") > mr.reduce("function(v) { return [] }", :keep => true)) > results in the same output. This, I'm unable to explain, unless the syntax for calling riak_kv_mapreduce:reduce_identity is incorrect in your example (I'm unfamiliar with Ripple's API). If I submit what I think is the equivalent query directly over HTTP or the Erlang console, I see the result come back as []. If the given syntax is incorrect, then it's likely generating another error that is causing the same behavior as described in Bugzilla issue 1185. > Can't a reduce phase appear before a map phase? A reduce phase *can* appear before a map phase, but not if the reduce phase is implemented in Javascript and the inputs are bucket-key pairs. Unfortunately, bucket-key pairs are represented as tuples that are not correctly converted to JSON, so evaluation of the phase fails. The typical workaround is as you attempted in your second example: using riak_kv_mapreduce:reduce_identity to alter the representation of bucket-key pairs (or implementing the reduce phase in Erlang instead). -Bryan _______________________________________________ riak-users mailing list riak-users@lists.basho.com http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
