adjusted-mr.js

m = function () {
    var events = [this._id];
    this.tags.forEach( function (z) {
        emit( z, {count:1, events: events} );
        });
}

r = function (key, values) {
    var total = 0;
    events = [];
    
    for (var i = 0; i < values.length; i++) {
        total += values[i].count;
        events.join(events, values[i].events);
    }
    
    return {count:total, events:events};
}