oids counter starts at zero; spec says it should be random

[dhasenan]

http://docs.mongodb.org/manual/reference/object-id/ says that the 'counter' field of an object ID should start at a random value. In oids.nim, it starts at 0.

I have a patch for this, and I'm using this issue to get approval from my workplace to commit to Nim.

[flaviut]

If your proposed fix uses math.random, it won't be a useful change. It'd essentially expand the clock value to 7 byes, 3 of which would be redundant.

[dhasenan]

That would only be true if the counter were re-randomized each time the clock changed, and even then not so much.

[dom96]

What's the status of this?

[andreaferretti]

The linked documentation reads

The 12-byte ObjectId value consists of:

    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.

but the implementation in oids.nim is

type
  Oid* = object ## an OID
    time: int32  ##
    fuzz: int32  ##
    count: int32 ##

where fuzz is random but fixed. This does not seem to be too compatible.

Either

• we update the oids module, or
• we declare and document that nim oids are unique but not mongo compatible, or
• we remove oids from the standard library

[andreaferretti]

I propose that we just remove from the documentation any link with mongodb, since the implementation is not compatible, but unique ids are useful anyway (notice that there is an external library for actual uuids though).

Mongo drivers can implement oids that are actually compatible with the spec

[Araq]

The module was written for Mongodb though and I ported the C code from it (it looks like Mongo later changed its implementation). No idea why we can't simply fix this and call it a day.

[timotheecour]

@Araq

The module was written for Mongodb though and I ported the C code from it (it looks like Mongo later changed its implementation). No idea why we can't simply fix this and call it a day.

that's tracked here: genOid has low entropy (creates lots of 0 bits) · Issue #9741 · nim-lang/Nim