猫鼬仅在不存在时插入

Question

So I don't seem to find anything about just inserting if the specified filter isn't found. I only find stuff on upserting documents but that's not what I want. I want to only insert something when that something isn't present in the collection

Answer 1

You should use update() with upsert: true , and then use the $setOnInsert instead of $set . It will insert if the filter does not find a match, otherwise it will do nothing.

Collection.update(
   filter,
   { $setOnInsert: update_object },
   { upsert: true }
)