Having a consistent relational db background, I always feel a bit lost about the patterns provided to associate models in no-sql land. Firebase db was 'weird' w

Having a consistent relational db background, I always feel a bit lost about the patterns provided to associate models in no-sql land. Firebase db was 'weird' when it came to associations, don't see that much changes here. The feature is available, but... Fire store provide 3 ways to do so, but why ? Going through the docs the results/benefits for each patterns remains unclear, the way to query each of those is not really understandable reading the docs. is this state will remains or is it a field that is potentially to be improved in the next releases ?