Question

How to Weigh mongoDB Data? For example, the following collection:

{"id":"1","name":"apple"}
 {"id":"2","name":"pear"}
 {"id":"3","name":"apple"}
 {"id":"4","name":"peach"}
 {"id":"5","name":"pear"}

Question:
Is to delete the repetition, the result is like this:

{"id":"1","name":"apple"}
 {"id":"2","name":"pear"}
 {"id":"4","name":"peach"}

Answer 1

Generally speaking, it is the result of deduplication rather than deletion from the database. To achieve this goal:

db.coll.aggregate([
 {$sort: {id: 1}},
 {$group: {_id: "$name", doc: {$first: "$$ROOT"}}},
 {$replaceRoot: {newRoot: "$doc"}}
 ]);

If you really want to delete, then all records that are not in this result can be deleted.