Let’s say I have this document: { "_id": objectId(), "products": [ { "product_id": "" } ] } I would like to make that the key product_id of documents in the array products must be unique for that document in the collection, (i don’t want it to affect other documents in the collection). I tried to… Read More Create an Index for a document inside array inside document in MongoDB

How to create a unique ID for each element of an array field, where uniqueness is maintained globally for all documents of the collection? Is it possible to specify create a unique index for this field? >Solution : You can make use of ObjectId data type. ObjectIds are 12-byte values that are guaranteed to be… Read More How to generate unique id for each element of an array field in MongoDB

Suppose that this is my compound index in my MongoDB collection: { "age": 1, "income": 1, } Will all returned records be sorted first by age and then by income? >Solution : That is not guaranteed. Each MongoDB node will return the documents in the order they are encountered. This means that if the query… Read More will documents be returned in the order of the compound index?