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How many BSON ObjectIds can a mongodb array field save

I am planning to save huge number of ids for foreignkey ids in this array. So, I am just checking what would be the max number of BSON::ObjectIds I can save in the field array. Lets say for example 

department_ids: [BSON::OBjectId('57cf6d6e8315292136000001'), BSON::OBjectId('57cf6d6e8315292136000002') ...... ]
Solution

  • 16MB is big enough to hold really large amount of ObjectId, ObjectIds aren't that heavy, they are 12 bytes and when you divide it by 16MB you get well beyond 1 million.

    But in case you still aren't assured, you can benefit by the flexible schema design of Mongo and create one follow-up document to hold further arrays and store the _id of that document in the concerned document with a field named as "followedBy" or something.

    downside is you will have to execute a follow-up query (or maybe not).

    Hope that helps.