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So that's it for this module.

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We had a detailed look at the aggregation framework and the stages and operators it offers.

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There are plenty of available stages and operators as you saw and I can only encourage you to dive into

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the official docs which are awesome and have detailed examples for all of them to explore them all and

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play around with them because playing around with them with some dummy data really is the best thing

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you can do here.

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Now stages define the different steps through which your data is funneled and each stage receives the

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output of the last stage as the input, except for the first stage which interacts directly with your

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collection and which therefore can take advantage of indexes and so on,

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so the first stage has like a special role.

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Also keep in mind that mongodb automatically optimizes your pipeline behind the scenes to for example

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match early,

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you should still try to write good code and a good set up of pipeline stages to efficiently query your

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data and query before you use sort or project to avoid unnecessary sorting or projections on all the

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data

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if you planned to filter it down anyways.

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Now operators can be used inside of stages and which operator can be used where depends on the stage

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and you can really just get a feeling for that overtime as you do work with all these operators, the

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official docs again help you with that as they describe use cases for all operators.

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Now there are a couple of important stages,

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the most common stages you will work with are probably match, group, project, sort, unwind.

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Now of course all the other stages are good too and you should definitely use whatever is the right tool for

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the job you're trying to get done but you'll work with these stages a lot,

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so you should definitely make sure that you've got this set and that you understand what they do.

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There also are some common behaviors that are shared between find filters and projection and match and

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project which are kind of the equivalence in the aggregation framework

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but keep in mind that in the aggregation framework, especially project is way more flexible and can do

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way more things like add new fields, recalculate, a lot of stuff that you can't do

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in the projection in the find method.

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So with that, I really encourage you to dive into the docs, pick some dummy data, maybe the data we use

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here or some other data and play around with these stages

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and these operators. This is the best way you can learn how to use the aggregation framework.