will a hashed index on _id be faster than the default b tree index that MongoDB creates?

Asked Jan 29 '23 at 19:57

Active Jan 29 '23 at 19:57

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hashed indexes, if evenly distributed, has time complexity of O(1), while b tree index always has complexity of O(log(N)).

So the question is, is the ObjectId that MongoDB creates for the _id field be evenly distributed such that the time complexity is indeed O(1)?

asked Jan 29 '23 at 19:57

The `_id` is a unique key, so the values cannot be evenly distributed. – Wernfried Domscheit Jan 29 '23 at 20:10
MongoDB stores all indexes in a b-tree, regardless of whether the valued is hashed or not. Check out https://stackoverflow.com/questions/28330170/mongodb-performance-difference-between-hash-and-ascending-indices-any-reason-no – Joe Feb 01 '23 at 01:55

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