Hi Daniel, this is due to a property of BSON ObjectIDs (which our backing database uses). The server will try to cast any incoming _id string to an objectID, and if successful, use the converted value. ObjectIDs can be created from 12 or 24 character strings, which is the reason the 12-characters _id strings you included are not working as you expect.
We are planning to migrate away from using ObjectIDs in the future, but until then, I recommend that if you require your own IDs, use strings of lengths other than 12 or 24 characters.
about 6 years ago
Ah 12 characters, nothing to do with - or _ . Thanks, I'll take that into account.