Streaming Aggregation

[whitfin]

It seems that there's no reason why aggregations can't be streamed, is there a chance support can be added for this?

[kofrasa]

Thanks for the question zackehh.

I did consider streaming aggregations early in the implementation, but then realized that it is not feasible due to $group and $sort operations which must operate on the entire collection.

The current streaming implementation for queries is not lazy and it was introduced to mimic MongoDB API interface so users can almost copy + paste code. That said, it is possible to do streaming subject to these constraints.

1. Ensuring the collection is immutable
2. Enforcing rules for streaming functionality (no $sort, $group etc)

Streaming can be implemented in one of two ways.

1. Using an iterator with chained functions
2. Using the new coroutine and/or generator functions in modern javascript.

Although I haven't settled on a position yet, there are some constraints I have place on the project to guide development. This include making Mingo a zero-dependency library and backward compatible for not too old browser version. So these will inform the implementation choice.

Please let me know whether this answers your question.

Thanks.

[kofrasa]

Added in v2.1.0. See https://github.com/kofrasa/mingo/wiki/API

[kofrasa]

For special cases ($sort, $group etc) the entire sequence is realized, processed, and a new iterator (stream object) is returned.