No problem. Unfortunately it is not documented. _p_client is the way pointer fields are stored inside MongoDB. createdAt should work also for facet, but clearly the conversion was not implemented for facet. Feel free to open a ticket in the repository.
Could you explain please how I must use match by pointer inside pipeline?
I have code like from my previouse question, and at once found that not only comparing by date does not work. equalTo also had no effect. I guess that I need move equalTo to date comparing to match stage inside pipeline, but I don’t know what is right syntax must be.
Because for date comparing { match: { createdAt: { $gt: DateObj } } } work fine by analogy I tried with { match: { pointerFieldName: { $eq: pointerObj } } } but without success. May be there are own tricks for that?
Thanks a lot, it’s working! At first I forget remove _ before my custom ClassName :), but then all was ok. Without your advice I never would’ve guessed about such syntax, earlier I only tried simple objectId.