Elena Grahovac

TODO: check that the fix fixed the problem mentioned in the issue

TODO: check that the fix fixed the problem mentioned in the issue

@AlekSi please decide about priority

Let's have one more test/examples with something where `$$ROOT` is used in at least two stages, e.g.: ``` db.coll.aggregate( [ {$addFields: {"new-field": "$$ROOT"}},{$addFields: {"new-field-1": "$$ROOT"}} ] ) ```

Let's add some tests with dot notation.

@AlekSi if INDEX SCAN is used, we should see it in `explain()`. That should be available without extra development. Still, it would be nice to have an example (insert enough...

I close this issue because INDEX SCAN will be visible in explain when it's used.

One more thing to check in the scope of this issue is if `collStats` command has the same problem: ``` db.runCommand({ collStats: "geospatial", scale: 1 }) ```

Let's also consider an example with `db.coll.aggregate( [ { $project: { "pampam" : "$v" } } ] )`

@kropidlowsky, your proposal sounds good to me! Please feel free to take this issue.