I read http://wiki.apache.org/solr/FieldCollapsing
and I tried the query http://192.168.0.1:8080/solr/append/select?q=mobile&group=true&group.field=brand
and I don't see the field collapsing. I mean I see the results, but not the grouping. My understanding is it should work, nothing to change in the solrconfig.xml ? In my schema, all my field are stored/index. My index is Lucene 2.9 and my Solr is 1.4.1. I don't see what I doing wrong...
Field collapsing is not available in Solr 1.4.1. You need Solr 3.3 or 4.0 (currently unreleased).
The wiki page about field collapsing also explains "If you haven't already, get a recent nightly build of Solr4.0 or Solr3.3..."
Look for "warning tags" in the Solr wiki that show when a particular feature is available only since a particular version of Solr:
来源：https://stackoverflow.com/questions/6455882/solr-field-collapsing