Can a MongoDB objectid contain only numbers?

Question

Can a MongoDB objectid contain only numbers?

There is a piece of code in a library that i'm using that does the following:

if (is_int($mixed) || ctype_digit($mixed)) {
    return;
}

And as a result it is throwing away a record in my DB with an ObjectId of '512417805115179054000022' because it only contains numbers.

Every other record has an ObjectId containing at least one alpha char such as '51241740511517a25b000017'

Is this a problem with the function that it assumes an ObjectId can never contain only numbers when it is in fact possible, or is it some lower level issue with a driver or something that has created an ObjectId with only numeric chars in error?

Answer 1

The regular expression used inside MongoDB to validate object ID's is /^[0-9a-fA-F]{24}$/

That means, an object ID can contain both numbers from 0-9 and uppercase or lowercase letters from a-f. And the ID will always have 24 characters. So an object ID with only numbers is as much possible as an object ID with only letters.

Answer 2

The ObjectId is BSON and you are seeing the HEXADecimal representation. So yes it is correct to assume that some IDs will not have letters.