I’m a Pivotal Labs developer at our NYC offices working on the Casebook development team. Casebook is a child-welfare-focused web application used by governments and non-profit organizations. Our users are social workers, caseworkers, and their leadership who work with children, families, and the broader community to provide services that ensure children are safe and healthy.
Search worries
Our users need to quickly find accurate information about the people on their workload to respond appropriately in crises and keep a high quality written record of their work with the children and families.
Solr powered Casebook’s initial search engine. Solr is built in Java, so we set up our application servers to run Java alongside our Ruby on Rails web application. We maintained a real-time copy of our important searchable data, such as people’s names, in our Solr index.
Our Solr-based approach ran into a few problems. Sometimes users would see outdated search results or, even worse, errors. This was annoying and also potentially damaging to our users’ ability to keep up with emergency situations.
Keeping our data synched in multiple locations caused most of our problems with Solr. Some of our more complex code paths would update the database but not propagate those changes to the search index. Users saw search-related error messages when there were communication problems with our Solr instances.
We had some fail-safes in place.
We wrote code that automatically restarted the Solr instances when they crashed. When we found the search data diverged from our application data, we manually rebuilt the search index to get the two data stores back in sync. These solutions just managed our problems rather than solving them.
These problems aren't unique to Solr. Other tools like Lucene, Ferret, and Sphinx have the same shortcomings when combined with Ruby on Rails.
Using the database itself as the search index
So the thought occurred to our team that we ought to try to make the database itself be the search index. We use a PostgreSQL database, and PostgreSQL 8.3 and later have built-in support for full-text search. PostgreSQL is a popular, mature SQL database solution that works great with Active Record. If you use Heroku, then you are already using a PostgreSQL 8.3 database that supports full-text search.
Since full-text search in PostgreSQL uses fairly complex SQL queries, we decided that the best approach would be to take advantage of Active Record's scopes. The idea is to make it easy to write code that looks like this:
Book.search_title("Ruby").include(:author).where("created_at > ?", 1.year.ago).limit(10)
So, I am proud to introduce pg_search, a Ruby gem that makes it easy to build search scopes that work just like this.