How to make unique username/user id/object?

[Joni Sebastian]

Maybe this question has been asked a lot, but i haven't found any post like that. Afaik, the solution to this particular problem with MongoDB depends on the language used.
What i'm trying to do was to make something like youtube, you know, with unique username and unique video id. How to do that with mgo?

[Ingo Gottwald]

Hi,

i don't think that this is language or driver specific question.

If you need something like uniqe IDs then mognodb offers its ObjectID that you can use - regardless of the driver.

As username that would be kind of hard to remember, so you could either use a unique index with some user-defined usernames which will give you annoying usernames like mine-is-already-taken345.

Or you choose the registrants e-mail address as username, which will always be unique when you verify it with a opt-in mail at registration.

But nothing of that is driver or language specific.

Regards

Ingo

[Joni Sebastian]

I heard the ObjectID is not that reliable as it will be a problem when you do the sharding or something.

[Ingo Gottwald]

Well the manual (http://docs.mongodb.org/manual/reference/object-id/) tells you something different:

ObjectId is a 12-byte BSON type, constructed using:

a 4-byte value representing the seconds since the Unix epoch,

a 3-byte machine identifier,

a 2-byte process id, and

a 3-byte counter, starting with a random value.

So with sharding you are on different machines and therefore you have different machine identifiers.

The warning in the reference is about time based ordering.

You should use other fields for that, like a timestamp.

[Joni Sebastian]

Thank you for the fast reply. I will try what you've advised.
But is there any other way?

[Ingo Gottwald]

There are always a lot of ways how to get things done.

Try to invent one. That's the joy of programing. :-)

2013/4/24 Joni Sebastian <pembala...@gmail.com>

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[Jim Robinson]

What I had read was that sharding based on the ObjectId was

ok for mixed read/write operations, but was not so good for

applications that mostly created new documents (e.g., say a

log entry database).  The reason being that the time component

of the ObjectId would tend to cause one node in the cluster to

become a hotspot for new documents.