One of the most common things to do in any standard rails web applications is auto-completion. One interesting solution to this is by using redis’ (which is blazing fast) sorted sets, storing key value pairs for partial matches. For example, if we wish to index the word ‘Dhruva Sagar’ (my name), you can simply create key -> value pairs of ‘d’ -> ‘Dhruva Sagar’, ‘dh’ -> ‘Dhruva Sagar’, ‘dhr’ -> ‘Dhruva Sagar’ and so on. Since hash lookups are of constant time complexity O(1), they’re very fast and hence the completions are too! Combine this with using sorted sets of redis to easily order / sort information on a specific criteria and you have a blazing fast solution. Of course the actual implementation can be further optimized by means of caching query results and make the system perform even further.
Soulmate is a cool gem by the guys at SeatGeek that provides a pretty cool implementation of the same. However it’s implementation wasn’t quite a good fit for my case since I wanted to work with a rails application and didn’t want to either host a separate server or mount the provided sinatra app inside of rails. I came across this nice post by Pat Shaughnessy – Finding your soulmate: autocomplete with Redis in Rails 3.1 which showcases how one can use the Soulmate gem and use it’s API to roll out your own auto-completion engine within your rails 3.1 application very easily.
This inspired me to fork Soulmate and extend it to build a Soulmate Rails gem over the weekend which provides a clean and intuitive API to do this from within Rails. Please do check it out, star it, fork it and use it to your hearts content . I’ve released it in alpha phase right now but it is fully usable with a reasonable test coverage. I’ll be contributing a lot to this, hopefully you find it useful too.
UPDATE : I released the first stable version 0.2.1, it should be usable as is without any issues.