Riak: query array of 2i through Map Reduce

Question

Can I query an array of secondary indexes in a Map Reduce job in Riak, instead of just the one key? I want to do something like this:

"inputs": {
    "bucket": myBycket,
        "index": "myIndex",
        "key": key + " OR " + key + " OR " + key
    },
    "query": [{
        "map": {
            "language":"javascript",
            "name":"Riak.mapValuesJson"
        }
    }]
}

But I have not found any support for it. The keys are in no particular order, so I don't think that I can use ranged queries.

Answer 1

You could certainly handle this with Map Reduce. If you presort your target keys, you could limit the range and possibly improve performance.

{
 "inputs": {
    "bucket": myBycket,
    "index": "myIndex",
    "start": firstkey,
    "end": lastkey
    },
    "query": [{
        "map": {
            "language":"javascript",
            "source":"function(v) {
                        if (v.key == "key1" || v.key == "key2") {
                           return [<<put what you want returned here>>]
                        } else {
                           return []
                        }
                      }"
        }
    }]
}

You should note that according to the docs site javascript Map Reduce has been officially deprecated, so you may want to use Erlang functions for new development.