Riak在MapReduce上排序

Question

function(values) { 
    return values.sort(
        function(a, b) {
            return b['timestamp'] - a['timestamp'];
        }
    );
}

I'm currently executing the above code for the reduce phase of a Riak MapReduce query but it is not correctly sorting by the value of timestamp key. Any ideas why?

I'm using the Riak Python client and this is the full code which contains the above reduce step:

query = riak_client.add('bucket')

query.map("function(v) { var data = JSON.parse(v.values[0].data); if (data.item == 'A') { return [[v.key, data]]; } return []; }")

query.reduce("function(values) { return values.sort(function(a, b) { return b['timestamp'] - a['timestamp']; }); }")

for result in query.run():
    print result

Answer 1

Try wrapping the return part in square brackets, effectively returning an array of results.

function(values) { 
  return values.sort(
    function(a, b) {
        return b['timestamp'] - a['timestamp'];
    }
  );
}

Have it look like this:

function(values) { 
  return [values.sort(
    function(a, b) {
        return b['timestamp'] - a['timestamp'];
    }
  )];
}