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solrgroupingfieldcollapsing

Alternate score-based sorting for Solr Grouping

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 .

Solution

  • Looks like this has been an open issue for a while: https://issues.apache.org/jira/browse/SOLR-2072 . This is exactly what I was talking about. I'll have to follow up with the Solr folks.