How to provide _id for unique key and how to migrate existing records

[steevej (Steeve Juneau)]

See a little example of custom _id from another thread:

Populating a collection using a custom field instead of _id

You simply set _id to any value. The only restriction is that it has to be unique within a collection. Some use UUID rather than generated ObjectId. For example, in mongosh: tlas atlas-d7b9wu-shard-0 [primary] test> c.insertOne( { _id : 0 } ) { acknowledged: true, insertedId: 0 } Atlas atlas-d7b9wu-shard-0 [primary] test> c.insertOne( { _id : new Date( "2023-01-31" ) } ) { acknowledged: true, insertedId: ISODate("2023-01-31T00:00:00.000Z") } Atlas atlas-d7b9wu-shard-0 [primary] test> c.inser…