Package org.apache.solr.search

Class CollapsingQParserPlugin

java.lang.Object
org.apache.solr.search.QParserPlugin
org.apache.solr.search.CollapsingQParserPlugin
All Implemented Interfaces:
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

  • Field Details

    • NAME

      public static final String NAME
      See Also:

    • HINT_TOP_FC

      public static final String HINT_TOP_FC
      See Also:

    • HINT_BLOCK

      public static final String HINT_BLOCK
      Indicates that values in the collapse field are unique per contiguous block, and a single pass "block based" collapse algorithm can be used. This behavior is the default for collapsing on the _root_ field, but may also be enabled for other fields that have the same characteristics. This hint will be ignored if other options prevent the use of this single pass approach (notable: nullPolicy=collapse)

      Do NOT use this hint if the index is not laid out such that each unique value in the collapse field is garuntteed to only exist in one contiguous block, otherwise the results of the collapse filter will include more then one document per collapse value.

      See Also:

    • COLLECT_ELEVATED_DOCS_WHEN_COLLAPSING

      public static String COLLECT_ELEVATED_DOCS_WHEN_COLLAPSING
      If elevation is used in combination with the collapse query parser, we can define that we only want to return the representative and not all elevated docs by setting this parameter to false (true by default).

  • Constructor Details

    • CollapsingQParserPlugin

      public CollapsingQParserPlugin()

  • Method Details

    • createParser

      public QParser createParser(String qstr, org.apache.solr.common.params.SolrParams localParams, org.apache.solr.common.params.SolrParams params, SolrQueryRequest request)
      Description copied from class: QParserPlugin
      Creates the QParser.
      Specified by:
      createParser in class QParserPlugin
      See Also:

    • getTopFieldCacheReader

      public static org.apache.lucene.index.LeafReader getTopFieldCacheReader(SolrIndexSearcher searcher, String collapseField)
      This forces the use of the top level field cache for String fields. This is VERY fast at query time but slower to warm and causes insanity.

    • rewriteSort

      public static org.apache.lucene.search.Sort rewriteSort(SortSpec sortSpec, org.apache.lucene.search.IndexSearcher searcher) throws IOException
      Helper method for rewriting the Sort associated with a SortSpec. Handles the special case default of relevancy sort (ie: a SortSpec w/null Sort object)
      Throws:
      IOException