Does this work?

[jonclawsonMeasurabl]

I can't install this. gem does not exist with running gem install rsql-ruby. Is there a way to install this?

[Strnadj]

I think it was never published to rubygems, but yes, check tests and eventually you could install that:

# Gemfile
gem "rsql-ruby", github: "eManPrague/rsql-ruby"