mongoose - MongoDB $pull efficiency -

let's assume following schema

var schema = new mongoose.schema({     data: { type: [number] } }); schema.index({ _id: 1, data: 1 }); var model = mongoose.model('test', schema); 

how efficient $pull operator when removing entries doc.data?

model.update({ _id: someid }, { $pull: { data: { $lte: 123 } } }).exec(); 

will use index , run in o(log n + m) complexity, n number of elements in data , m number of removed elements? or have scan whole array?

and what's complexity of removing element after mongo finds it? o(1), o(log n) or o(n) has shift other items?

the collection's indexes used doc finding part of update, not update itself.

so built-in index on _id used find document, $pull update require whole data array read , scanned against {$lte: 123} query: o(n).

the index added on { _id: 1, data: 1 } used if included data in actual query as:

model.update({_id: someid, data: {$lte: 123}}, {$pull: {data: {$lte: 123}}}).exec(); 

but provide benefit in case data contained no elements value <= 123 short-circuiting update doc no longer match criteria. still wouldn't used find data elements $pull itself.