Is it bad to change _id type in MongoDB to integer?

Question

MongoDB uses ObjectId type for _id.

Will it be bad if I make _id an incrementing integer?

(With this gem, if you\'re interested)

Answer 1

I had a use case for this: replacing _id with a 64 bit integer that represented a simhash of a document index for searching.

Since I intended to "Get or create", providing the initial simhash, and creating a new record if one didn't exist was perfect. Also, for anyone Googling, MongoDB support explained to me that simhashes are absolutely perfect for sharding and scaling, and even better than the more generic ObjectId, because they will divide up the data across shards perfectly and intrinsically, and you get the key stored for negative space (a uint64 is much smaller than an objectId and would need to be stored anyway).

Also, for you Googlers, replacing a MongoDB _id with something other than an objectId is absolutely simple: Just create an object with the _id being defined; use an integer if you like. That's it: Mongo will simply use it. If you try to create a document with the same _id you'll get an error (E11000/Duplicate key). So like me, if you're using simhashing, this is ideal in all respects.