[SERVER-31760] Lookup sub-pipeline is not using index for equality match - MongoDB Jira

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Backwards Compatibility:
Fully Compatible
Operating System:
ALL
Backport Requested:

v3.6
Sprint:
Query 2017-11-13, Query 2017-12-04, Query 2017-12-18, Query 2018-01-01, Query 2018-01-15
Linked BF Score:
0

I am doing following aggregation to join two collection using foreign pipeline.
It seems match stage is not using index at all.

db.blogpost.aggregate([

  { $lookup: {

    from: 'comment',

    let: { blogpost_id: "$_id" },

    pipeline: [ {

       $match: { $expr: { $eq: [ "$blogpost.id", "$$blogpost_id"] } }

    } ],

    as: 'comments'

}}

])

is documented by

DOCS-11203 Docs for SERVER-31760: Lookup sub-pipeline is not using index for equality match

is duplicated by

SERVER-32826 Lookup Pipeline issue performance is very bad in more records

SERVER-33364 Combined $match, $expr in aggregation not using indexes

related to

SERVER-31804 $expr rewrite optimization can lead to incorrect query results

Participants:: aniket, Asya Kamsky, David Storch, Githook User, James Wahlin, Naveen, Trevor Wilson