Currently, solr grouping (http://wiki.apache.org/solr/FieldCollapsing) sorts groups "by the score of the top document within each group". E.g.
[...] "groups":[{ "groupValue":"81cb63020d0339adb019a924b2a9e0c2", "doclist":{"numFound":9,"start":0,"maxScore":4.729042,"docs":[ { "id":"7481df771afe39fab368ce19dfeeb528", [...], "score":4.729042}, { "id":"c879e95b5f16343dad8b1248133727c2", [...], "score":4.6635237}, { "id":"485b9aec90fd3ef381f013c51ab6a4df", [...], "score":4.347174}] }}, [...] Is there an out-of-the-box way to instead sort groups by the sum of the scores of the documents within each group? E.g. [...] "groups":[{ "groupValue":"81cb63020d0339adb019a924b2a9e0c2", "doclist":{"numFound":9,"start":0,*"scoreSum":13.739738*,"docs":[ { "id":"7481df771afe39fab368ce19dfeeb528", [...], "score":4.729042}, { "id":"c879e95b5f16343dad8b1248133727c2", [...], "score":4.6635237}, { "id":"485b9aec90fd3ef381f013c51ab6a4df", [...], "score":4.347174}] }}, [...] With the release of sorting by Function Query ( https://issues.apache.org/jira/browse/SOLR-1297), it seems that there should be a way to use the sum() function ( http://wiki.apache.org/solr/FunctionQuery). But it's not quite close enough since the "score" field is not part of the documents. I feel like I'm close but I'm missing some obvious piece. I'm using Solr 3.5. Thank you in advance for your time.