I was trying to see how mongo works with relations via it's aggregations framework
I have 3 collections, related by ObjectId: photos (~300 000 records)report <- photo_reports(~3000) <- places(~300). All requests were made by MongoChef (gui)

From time to time MongoDB goes out with segfault errors in log (is attached). I noticed that with "preserveNullAndEmptyArrays: false" the same request works ok. But maybe this is just a coincidence.