Constructor Detail

• TermFirstPassGroupingCollector

  public TermFirstPassGroupingCollector​(String groupField,
                                        org.apache.lucene.search.Sort groupSort,
                                        int topNGroups)
                                 throws IOException

  Create the first pass collector.

  Parameters:

  groupField - The field used to group documents. This field must be single-valued and indexed (FieldCache is used to access its value per-document).

  groupSort - The Sort used to sort the groups. The top sorted document within each group according to groupSort, determines how that group sorts against other groups. This must be non-null, ie, if you want to groupSort by relevance use Sort.RELEVANCE.

  topNGroups - How many top groups to keep.

  Throws:

  IOException - When I/O related errors occur

Method Detail

• getDocGroupValue

  protected String getDocGroupValue​(int doc)

  Description copied from class: AbstractFirstPassGroupingCollector
  Returns the group value for the specified doc.

  Specified by:

  getDocGroupValue in class AbstractFirstPassGroupingCollector<String>

  Parameters:

  doc - The specified doc

  Returns:

  the group value for the specified doc

• copyDocGroupValue

  protected String copyDocGroupValue​(String groupValue,
                                     String reuse)

  Description copied from class: AbstractFirstPassGroupingCollector
  Returns a copy of the specified group value by creating a new instance and copying the value from the specified groupValue in the new instance. Or optionally the reuse argument can be used to copy the group value in.

  Specified by:

  copyDocGroupValue in class AbstractFirstPassGroupingCollector<String>

  Parameters:

  groupValue - The group value to copy

  reuse - Optionally a reuse instance to prevent a new instance creation

  Returns:

  a copy of the specified group value

• setNextReader

  public void setNextReader​(org.apache.lucene.index.IndexReader reader,
                            int docBase)
                     throws IOException

  Overrides:

  setNextReader in class AbstractFirstPassGroupingCollector<String>

  Throws:

  IOException