I have just released a small library that help to build query from a map with structure similar to Mongo DB filter like this:

Filtery.apply(Post, %{name: {:like, "elixir"}, is_draft: false, tags: {:has, "ecto"} })

Here is the repo:

https://github.com/bluzky/filtery

It’s quite simple and supports filtering on a single table only.
It supports basic operators eq, :gt, :gte, :in, :lt, :lte, :ne, :nin, :and, :or and some other helpful operators. And you can define your own operators too.

Please try and leave your feedback. Thank you.

Update v0.2.0

I have added a special operator ref to join multiple table

query = Filtery.apply(Post, %{comments: {:ref, %{
                                    approved: true,
                                    content: {:like, "filtery"}
                                 }}})

comments field must be the association name in your Post schema