Apache Solr Reference Guide Covering Apache Solr 6.0

q=foo&fq={!collapse field=ISBN}&expand=true
The “expand=true” parameter turns on the ExpandComponent. The ExpandComponent adds a new section to
the search output labeled “expanded”.
Inside the expanded section there is a map with each group head pointing to the expanded documents that are
within the group. As applications iterate the main collapsed result set, they can access the expanded map to
retrieve the expanded groups.
The ExpandComponent has the following parameters:
Parameter Description Default
expand.sort Orders the documents within the expanded groups score
desc
expand.rows The number of rows to display in each group 5
expand.q
Overrides the main q parameter, determines which documents to include in the
main group.
main q
expand.fq Overrides main fq's, determines which documents to include in the main group. main fq's
Result Clustering
The clustering (or cluster analysis) plugin attempts to automatically discover groups of related search hits
(documents) and assign human-readable labels to these groups. By default in Solr, the clustering algorithm is
applied to the search result of each single query—this is called an on-line clustering. While Solr contains an
extension for for full-index clustering ( off-line clustering) this section will focus on discussing on-line clustering
only.
Clusters discovered for a given query can be perceived as dynamic facets. This is beneficial when regular
faceting is difficult (field values are not known in advance) or when the queries are exploratory in nature. Take a
look at the Carrot2 project's demo page to see an example of search results clustering in action (the groups in
the visualization have been discovered automatically in search results to the right, there is no external
information involved).
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