2013/7/29 Norbert Hartl <norbert@hartl.name>:
Am 29.07.2013 um 15:46 schrieb "Esteban A. Maringolo" <emaringolo@gmail.com>:
Is it a good practice to use the OID value (anInteger) as an
"external" identifier of your domain object?
...
I like OID/UUIDs, and I don't want to duplicate that logic in my app.
I think for your purpose OID will be fine but I'm not sure. I use UUIDs. You can instruct mongo to use a UUID instead of an OID. Works flawlessly.
How do you do that? Because OID's are a BSON native artifact,
efficient in terms of storage and lookup (a 12 byte integer in the
end...)
Is there a way to have an smaller UUID? more like the first eight
chars of a Git commit or similar�
If you look at [1] you can see that UUID is a native BSON artefact as well. Pharo has a UUID class. I extended the Mongo driver to serialize UUID properly. So basically all you need is to put a UUID object in your model object and serialization should be automatic. Of course you need to tell the serialization layer to serialize it as _id. But it is fully supported on mongo. Performance wise it is said it might be a tad slower than object ids. But if you have doubts about object ids you should be willing to take the payoff. I can't help here much because I have my own serialization layer that is pretty much superseded by Voyage.
Do you have really performance problems why you like to restrict the key size? That would be a bad because you would restrict the uniqueness to a useless artefact. IIRC mongo does that for you anyway. There is a certain size of key mongo evaluates first and rechecks on collision. But I'm not sure I had only the impression the same techniques are in charge as for other hashing problems.
hope this helps,
Norbert