MongoDB Shell: Query BinData by Type

Question

I am trying to query a large collection by the _id field which uses BinData.

Some of these ids use BinData of type 4:

"_id" : BinData(4,"CNDF66qIlCY92q1vFAAAAQ==")

While some use BinData of type 3:

"_id" : BinData(3,"CNDF66qJ29g92q1vFAAAEw==")

I need to find all of the _id fields that have BinData.type = 3 and was wondering if anyone has had luck querying like this in the MongoDB shell.

Any help would be greatly appreciated!

Answer 1

You can do this with a $where style query as the BinData object has a .subtype() method that returns that "type":

db.collection.find(function(){ return this._id.subtype() == 3 })

Note that the "type" 3 BinData is by default what would be generated by the new UUID helper available to the shell from MongoDB 2.6:

UUID("0123456789abcdeffedcba9876543210")
BinData(3,"ASNFZ4mrze/+3LqYdlQyEA==")