Automatic Aggregate Event Stream filtering

[smcvb]

Enhancement Description

When retrieving a stream of events for a given aggregate, chances are high not all events in the stream will actually be used to source the aggregate. Adding the unused events as a filter for subsequent calls will make aggregate event stream retrieval more efficient. It does require specific implementations on the storage engines to actually store and use a provided filter.

Current Behaviour

Aggregate event streams are always completely retrieved without any filter.

Wanted Behaviour

Filter out unused events for sourcing the aggregate from the event stream on subsequent invocations.

[smcvb]

I believe the introduction of the Dynamic Consistency Boundary (DCB), as suggested in the presentation The Aggregate is dead! Long live the Aggregate!, will be of utmost importance to provide a way to easily filter events for any aggregate stream format.

Hence, I anticipate that once the DCB idea has matured more, that Axon Framework may just provide a similar solution.
Given that supporting the DCB will be a very (very!) rough change for the EventStore, it will very likely be an Axon Framework 5 feature.
Simply because of the breaking changes it'll introduce.

To that end, I have added this issue to milestone 5.0.0.
Note that this does not conclusively mean it'll be a part of 5.0.0, but rather part of the Axon Framework 5.x lifecycle.