I have a collection of around 3m rather small documents. Total size of collection is <1GB.

If I do a text search for a word that is present in many (~1.5m) documents (i.e. it finds almost all the documents) it takes some time but I get the results.

If I also add `{ $sort:

}` to sort by relevance it starts to consume memory like crazy effectively crashing the machine almost instantly.

What may be wrong? Where to look?

An interesting point: The whole database I am talking about would fit into our memory three fold.

We were monitoring the memory consumption when the problem occurs. The system had 58% percent free memory one second. It dropped to 10 % free memory in one second. And than it crashed.

Our version is 5.0.18