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Add FAQ about slow joins #320

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1 change: 1 addition & 0 deletions docs/source/conf.py
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Expand Up @@ -45,6 +45,7 @@
"pymongo": ("https://pymongo.readthedocs.io/en/stable/", None),
"python": ("https://docs.python.org/3/", None),
"atlas": ("https://www.mongodb.com/docs/atlas/", None),
"manual": ("https://www.mongodb.com/docs/manual/", None),
}

root_doc = "contents"
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13 changes: 13 additions & 0 deletions docs/source/faq.rst
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Expand Up @@ -4,6 +4,19 @@ FAQ

This page contains a list of some frequently asked questions.

Performance
===========

Querying across relational fields like :class:`~django.db.models.ForeignKey` and :class:`~django.db.models.ManyToManyField` is really slow. Is there a way to improve the speed of these joins?
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Not really. Joins use MongoDB's :doc:`$lookup
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Re: "Not really."

We could mention the possibility of using raw_aggregate() to manually construct a query as mentioned in #309, but I think that's unlikely to be an attractive and maintainable solution for most projects.

<manual:reference/operator/aggregation/lookup>` operator, which doesn't perform
well with large tables.

The best practice for modeling relational data in MongoDB is to instead use
:doc:`embedded models <topics/embedded-models>`.

Troubleshooting
===============

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