You can connect drupal with an apche solr server to index content and use advanced search features (faceted search, "more like this"-block,...). But for a recent project I needed to go that extra mile and write some code to use extra features of solr. The outcome: two new modules.
- Apachesolr_location This module makes it possible to index coordinates from a location field. In the future it will also extend the apachesolr search box to do geospatial search.
- Apachesolr_saved_searches This is still a sandbox, but in heavy development. This module will make it possible to save a solr query, to execute it again later, or to give alerts when new items are available for that search.

When creating the functionality and refactoring it as drupal modules, I had to search for documentation, dive into the api of apachesolr. I will share my experience. And I hope this will help people to make their own extension modules.