func (q *Query) SetMaxScan(n int) *Query {
	q.m.Lock()
	q.op.options.MaxScan = n
	q.op.hasOptions = true
	q.m.Unlock()
	return q
}
func (q *Query) SetMaxScan(n int) *Query {
	q.m.Lock()
	q.op.options.MaxScan = n
	q.op.hasOptions = true
	q.m.Unlock()
	return q
}
// SetMaxScan constrains the query to stop after scanning the specified
// number of documents.
//
// This modifier is generally used to prevent potentially long running
// queries from disrupting performance by scanning through too much data.