Class CollapsingQParserPlugin

  extended by
      extended by
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

Nested Class Summary
static class CollapsingQParserPlugin.CollapseScore
 class CollapsingQParserPlugin.CollapsingPostFilter
Nested classes/interfaces inherited from interface org.apache.solr.core.SolrInfoMBean
Field Summary
static String NAME
static String NULL_COLLAPSE
static String NULL_EXPAND
static String NULL_IGNORE
Fields inherited from class
DEFAULT_QTYPE, standardPlugins
Constructor Summary
Method Summary
 QParser createParser(String qstr, SolrParams localParams, SolrParams params, SolrQueryRequest request)
          return a QParser
 void init(NamedList namedList)
Methods inherited from class
getCategory, getDescription, getDocs, getName, getSource, getStatistics, getVersion
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail


public static final String NAME
See Also:
Constant Field Values


public static final String NULL_COLLAPSE
See Also:
Constant Field Values


public static final String NULL_IGNORE
See Also:
Constant Field Values


public static final String NULL_EXPAND
See Also:
Constant Field Values
Constructor Detail


public CollapsingQParserPlugin()
Method Detail


public void init(NamedList namedList)


public QParser createParser(String qstr,
                            SolrParams localParams,
                            SolrParams params,
                            SolrQueryRequest request)
Description copied from class: QParserPlugin
return a QParser

Specified by:
createParser in class QParserPlugin

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