This module offers a simple and performant but not perfect way to recognize and group seemingly duplicate records. It uses Apache Solr's grouping feature. Solr groups all records with the same matchkey, when called with the grouping params below. The first of this similar records in each group is called "head record" the others are referred as "subrecords". Grouping can optionally be turned on or off by end-users. The last state is being saved as cookie. This makes it easy to compare and evaluate grouping.