leopd

function add_rand_field(collection) {
    collection.find().forEach(function(data) {
        collection.update({_id:data._id}, {
          $set:{rand:Math.random()}
        });
    });
    collection.ensureIndex({rand:1},{background:true})
}

leopd

[alias]
    lgb = log --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset%n' --abbrev-commit --date=relative --branches

leopd

count_by = function(collection,field) {
    return collection.aggregate({
        $group: {
            _id: "$" + field,
            count: { $sum: 1 }
        }
    })
}
 
count_by(db.vid10,'char');