This is great. I had a feeling something like this was coming given most firebase people were pretty open about what the shortcomings of the Realtime DB were and AngularFire received some much needed attention to its database API last week.
That said, I really hope there are plans for some full text search ability beyond the current suggestions[1]. I would very much like to ditch Elasticsearch in favor of db engine provided search. Even a small subset of the Elasticsearch/Solr feature set (similar to the full text search capability now available for Postgres[2]) would be a very welcome addition.
[1] https://firebase.google.com/docs/firestore/solutions/search [2] https://www.postgresql.org/docs/9.5/static/textsearch.html