Apache Solr’s result grouping feature is now a widely used feature. The major drawback was that grouping was not supported for distributed searches which also know as sharding in Solr. The good news is that recently distributed grouping has been added to Solr! It has been added the trunk and the stable branch (branch3x). This means that distributed grouping will be included in the upcoming Solr 3.5 and Solr 4.0 release.