Features<p>Real-time search
High performance
Segment words search and prefix match search
Support ActiveRecord and Mongoid
Sort results by one field
Homophone search, pinyin search
Conditions support
1. you are already using Redis for some other part of the application
2. you don't want yet to have Lucene/Solr/ElasticSearch
3. you don't need to support too advanced searches
On the other hand while building such a library could be a good learning exercise, I think that before using it in an application you should look for other already existing libraries and try to collaborate with the original authors.