Description

Hi!

This page https://docs.mongodb.com/manual/reference/operator/aggregation/sort/#sort-operator-and-performance has a list of operators that should be used before using `$sort` at the bottom section of the page, namely `$project`, `$unwind`, and `$group`

asya pointed out that this list is incomplete, when she took a look at our in-person training, which is largely based on the documentation.

Making this ticket to bring attention to this. Is there a definitive list that should be put on the documentation page? I would love to know, so that I can also update the in-person training accordingly.

Thank you!

Scope of changes

• Investigate performance relationships between $sort and other aggregation stages in context of index usage
• Document any missing operators
• $sort can only use indexes if it is the first pipeline stage or if after all $match stages.