Array Return from Reduce

[J Singh]

The Map/Reduce documentation says: "Currently, the return value from a reduce function cannot be an array (it's typically an object or a number)."

Does anyone have a suggestion on how we might be able to implement it with Mongo 1.8x? This is what we are trying to accomplish, although it doesn't work because of the above restriction.

map = function() { emit(this.FnName, [this.FnAddress]); }

red = function(k,v) { var addrs=[]; for (var i in v) var addr = v[i][0]; if(addrs.indexOf(addr) < 0)addrs.push(addr); return addrs;}

res = db.MyColl.mapReduce(map, red, {query: { "Timestamp" : { $gte: 1, $lte: 15 } }, out: "slice_fn_addrs"})

Thanks.

[Nat]

you just wrap it inside an object something like:

map = function() { emit(this.FnName, { "arr" : this.FnAddress]); }

red = function(k,v) { var addrs=[]; for (var i in v.arr) var addr = v.arr[i][0]; if(addrs.indexOf(addr) < 0)addrs.push(addr); return { "arr" : addrs };}

[Scott Hernandez]

You can put it in an object/doc as the documentation suggests:

map:
...
emit(this.FnName, {addresses: [this.FnAddress]});

reduce:
...
return {addresses: addrs}

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