This ticket covers any necessary code changes and testing for two kinds of queries: sub-pipelines (e.g. the subpipeline run by $lookup or $graphLookup against the foreign collection) and pipeline prefixes, meaning the parts of the agg pipeline which are handled by the find layer.

We may be able to support these queries if the sub-pipeline or pipeline prefix is entirely supported in CQF. But, the user story is confusing and it adds to the testing surface area. This ticket may not result in any code changes but we should verify that we use the classic query system.