I have a collection with feeds. The documents are structured something like this:
{
_id: '123',
title: 'my title',
openedBy: ['321', '432', '543'] // ID of users
}
Then I have users:
{
_id '321',
friends: ['432'] // ID of users
}
What I would like to accomplish is to get the number of friends that has opened the feeds fetched by the user. I do this now with a mapReduce, passing the friends of the user fetching the feeds. I do not think I am doing it correctly as I reduce by only returning the emit itself and I have to convert the result back to a normal query result on the finalizer:
db.collection(collectionName).mapReduce(function () {
var openedByFriendsLength = 0;
for (var x = 0; x < friends.length; x++) {
if (this.openedBy.indexOf(friends[x]) >= 0) {
openedByFriendsLength++;
}
}
emit(this._id, {
title: this.title,
openedByLength: this.openedBy.length,
openedByFriendsLength: openedByFriendsLength
});
}, function (key, emits) {
return emits[0];
}, {
out: 'getFeeds',
scope: {
friends: user.friends
},
}, function (err, collection) {
collection.find().toArray(function (err, feeds) {
// Convert the _id / value to a normal find result
var resultFeeds = [];
for (var x = 0; x < feeds.length; x++) {
resultFeeds.push(feeds[x].value);
resultFeeds[resultFeeds.length - 1]._id = feeds[x]._id;
}
callback(err, resultFeeds);
});
});
I have looked at aggregation, but I can not quite figure out how to do the same thing. Or is the structure of the documents here all wrong?
Thanks for any reply!