Add support for $elemMatch find query operator

[jpx]

Hi,

I would like to see $elemMatch find query (array) operator implemented in LinvoDB and am willing to contribute to it.
However, I am not sure where to start as there already is implementation for array of sub-queries ($and, $or...) but not for sub-queries on array fields ($elemMatch for instance, see https://docs.mongodb.com/manual/reference/operator/query/#array).

Do you have any leads to implement it ?

It is documented here https://docs.mongodb.com/manual/reference/operator/query/elemMatch/.

Edit: I might actually have a simple solution here, however it does not use indexes at all. Some more work is involved to run fully indexed $elemMatch queries.