Live Query Event
Describes the different types of event that you can receive when dealing with live queries.
Initial: The first event that will be delivered and it will only be delivered once.
Update: This event will be delivered each time the results of the provided query change. It contains information about the set of documents that previously matched the query before the update, along with information about what documents have been inserted, deleted, updated, or moved, as part of the set of matching documents.
Provides information about the changes that have occurred in relation to a live query for a given update event.