MongoDB Map Reduce -- Sum Array

[rmarut]

 

Hi,

I have MongoDB shell 2.1.1

I have a Collection with elements Things, Value, List: where List is an N+ Array

of Strings, i.e.

"Things" : "Function", "Value" : "Element", "List" : ["loc1", "loc2","loc3]

 

simple to sum List by key: Things, Value on mongodb shell:

db.report.find().forEach( function(feature) { print(feature.feature + " " +

feature.value + " " + feature.processes.length); });

 

returns:

 

{ "result" : [{

"_id" : {

"Things" : "Function",

"value" : "Element" },

"List" : 3}, ],

"ok" : 1

}

 

I have not been able to execute this from ireports.

This is the MapReduce function I am executing:

{

'collectionName' : 'report',

},

'mapReduce' : {

'map' : 'function () {

emit ({thing:this.Things,val:this.Value}, {count : this.List});

}',

'reduce' : 'function (key, values) {

var total = 0;

for (index i = 0; i < values.length; i++){

total += values[i}.List;;

}

return {total : values[i}.List;}

}',

 

'out' : 'totalList'

}

}

 

returns:

_id.Things_____id.Value_____List

Function_________Element___loc1,loc2,loc3

 

Please tell me how I can return a count of List and not the values of List.

Can anyone assist??

 

Post Edited by rmarut at 05/17/2012 18:35