org.apache.solr.search

Class CollapsingQParserPlugin

  • All Implemented Interfaces:
    SolrInfoMBean, NamedListInitializedPlugin


    public class CollapsingQParserPlugin
    extends QParserPlugin
    The CollapsingQParserPlugin is a PostFilter that performs field collapsing. This is a high performance alternative to standard Solr field collapsing (with ngroups) when the number of distinct groups in the result set is high.

    Sample syntax:

    Collapse based on the highest scoring document:

    fq=(!collapse field=field_name}

    Collapse based on the min value of a numeric field:

    fq={!collapse field=field_name min=field_name}

    Collapse based on the max value of a numeric field:

    fq={!collapse field=field_name max=field_name}

    Collapse with a null policy:

    fq={!collapse field=field_name nullPolicy=nullPolicy}

    There are three null policies:
    ignore : removes docs with a null value in the collapse field (default).
    expand : treats each doc with a null value in the collapse field as a separate group.
    collapse : collapses all docs with a null value into a single group using either highest score, or min/max.

    The CollapsingQParserPlugin fully supports the QueryElevationComponent