If true, the result of the first field grouping command is used as the main result list in the response, using group.format=simple.

public SolrQuery SolrQuery::setGroupMain ( string $value )

SolrQuery::setGroup() - Enable/Disable result grouping (group parameter)
SolrQuery::addGroupField() - Add a field to be used to group results.
SolrQuery::addGroupFunction() - Allows grouping results based on the unique values of a function query (group.func parameter).
SolrQuery::addGroupQuery() - Allows grouping of documents that match the given query.
SolrQuery::addGroupSortField() - Add a group sort field (group.sort parameter).
SolrQuery::setGroupFacet() - Sets group.facet parameter
SolrQuery::setGroupOffset() - Sets the group.offset parameter.
SolrQuery::setGroupMain()
SolrQuery::setGroupNGroups() - If true, Solr includes the number of groups that have matched the query in the results.
SolrQuery::setGroupTruncate() - If true, facet counts are based on the most relevant document of each group matching the query.
SolrQuery::setGroupFormat() - Sets the group format, result structure (group.format parameter).
SolrQuery::setGroupCachePercent() - Enables caching for result grouping

SolrQuery::setGroupMain