https://medium.com/@topspinj/country-drop-down-list-92e6f3552f58
Select2 is a jQuery based replacement for select boxes. It supports searching, remote data sets, and infinite scrolling of results.
The select2-rails gem integrates the Select2 jQuery plugin with the Rails asset pipeline.
https://github.com/argerim/select2-rails
Search and Autocomplete in Rails Apps
https://www.sitepoint.com/search-autocomplete-rails-apps/
pg_search builds ActiveRecord named scopes that take advantage of PostgreSQL’s full text search