How to search through a collection?

Question

MongoDB

In the collection there are documents of the form {_id: id, "custom-field": true} or just {_id: id}
Do I correctly select all values ​​where custom-field = true, or it does not exist at all.
db.collection.find({"custom-field": {$in: [true]}}) - When you need to select documents where there is custom-field = true
db.collection.find({"custom-field": { $nin: [true]}}) - All other documents where custom-field is absent or false
One more question: I heard that skip in mongodb is not very fast, is it? I will need to iterate over a collection with 20 million documents, I think to select them by 1000 and skip or is this a bad idea? Or if I select 20KK documents at once and put them into an array, then if there is RAM, everything will work well? Or is it not worth it at all?

Answer 1

db.collection.find({"custom-field": {$in: [true]}})

db.collection.find({"custom-field": true})
db.collection.find({"custom-field": {$ne: true}})
It does not work very fast everywhere, the specifics of tree indexes. Therefore, it is better to use a sorting field for pagination, then it will be fast, for example {_id: {$gt: lastReceivedID}}