MongoDB map reduce count giving more results than a query
- by giorgiosironi
I have a collection users in Mongo and I execute this map reduce which I believe is the equivalent of a COUNT(*) GROUP BY origin:
> m = function() { for (i in this.membership) {
... emit( this.membership[i].platform_profile.origin, 1 );
... } }
function () {
for (i in this.membership) {
emit(this.membership[i].platform_profile.origin, 1);
}
}
> r = function( id, values ) { var result = 0;
... for ( var i = 0; i < values.length; i ++ ) { result += values[i]; }
... return result; }
function (id, values) {
var result = 0;
for (var i = 0; i < values.length; i++) {
result += values[i];
}
return result;
}
> db.users.mapReduce(m, r, {out : { inline: 1}});
{
"results" : [
{
"_id" : 0,
"value" : 15
},
{
"_id" : 1,
"value" : 449
},
...
}
But if I try to count how many documents have this field set to a specific value like 1, I get fewer results:
db.users.count({"membership.platform_profile.origin": 1});
424
What am I missing?
