SolrQuery::setGroupLimit() - Specifies the number of results to return for each group. The server default value is 1
SolrQuery::setGroupMain() - If true, the result of the first field grouping command is used as the main result list in the response, using group.format=simple
SolrQuery::setGroupTruncate() - If true, facet counts are based on the most relevant document of each group matching the query