So that's it for this module.
We had a detailed look at the aggregation framework and the stages and operators it offers.
There are plenty of available stages and operators as you saw and I can only encourage you to dive into
the official docs which are awesome and have detailed examples for all of them to explore them all and
play around with them because playing around with them with some dummy data really is the best thing
you can do here.
Now stages define the different steps through which your data is funneled and each stage receives the
output of the last stage as the input, except for the first stage which interacts directly with your
collection and which therefore can take advantage of indexes and so on,
so the first stage has like a special role.
Also keep in mind that mongodb automatically optimizes your pipeline behind the scenes to for example
match early,
you should still try to write good code and a good set up of pipeline stages to efficiently query your
data and query before you use sort or project to avoid unnecessary sorting or projections on all the
data
if you planned to filter it down anyways.
Now operators can be used inside of stages and which operator can be used where depends on the stage
and you can really just get a feeling for that overtime as you do work with all these operators, the
official docs again help you with that as they describe use cases for all operators.
Now there are a couple of important stages,
the most common stages you will work with are probably match, group, project, sort, unwind.
Now of course all the other stages are good too and you should definitely use whatever is the right tool for
the job you're trying to get done but you'll work with these stages a lot,
so you should definitely make sure that you've got this set and that you understand what they do.
There also are some common behaviors that are shared between find filters and projection and match and
project which are kind of the equivalence in the aggregation framework
but keep in mind that in the aggregation framework, especially project is way more flexible and can do
way more things like add new fields, recalculate, a lot of stuff that you can't do
in the projection in the find method.
So with that, I really encourage you to dive into the docs, pick some dummy data, maybe the data we use
here or some other data and play around with these stages
and these operators. This is the best way you can learn how to use the aggregation framework.