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## org.apache.lucene.search.grouping
Class AbstractSecondPassGroupingCollector<GROUP_VALUE_TYPE>

    java.lang.Object
      org.apache.lucene.search.Collector
          org.apache.lucene.search.grouping.AbstractSecondPassGroupingCollector<GROUP_VALUE_TYPE>

Direct Known Subclasses:
  TermSecondPassGroupingCollector

    public abstract class AbstractSecondPassGroupingCollector<GROUP_VALUE_TYPE>

extends Collector

SecondPassGroupingCollector is the second of two passes necessary to collect grouped docs. This pass gathers the top N documents per top group computed from the first pass. Concrete subclasses define what a group is and how it is internally collected.

See `org.apache.lucene.search.grouping` for more details including a full code example.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary
`class` | `AbstractSecondPassGroupingCollector.SearchGroupDocs<GROUP_VALUE_TYPE>`

Field Summary
`protected AbstractSecondPassGroupingCollector.SearchGroupDocs<GROUP_VALUE_TYPE>[]` | `groupDocs`
`protected Map<GROUP_VALUE_TYPE,AbstractSecondPassGroupingCollector.SearchGroupDocs<GROUP_VALUE_TYPE>>` | `groupMap`

Constructor Summary
`AbstractSecondPassGroupingCollector(Collection<SearchGroup<GROUP_VALUE_TYPE>> groups, Sort groupSort, Sort withinGroupSort, int maxDocsPerGroup, boolean getScores, boolean getMaxScores, boolean fillSortFields)`

Method Summary
`boolean` | `acceptsDocsOutOfOrder()` Return `true` if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) to `Collector.collect(int)`.
`void` | `collect(int doc)` Called once for every document matching a query, with the unbased document number.
`TopGroups<GROUP_VALUE_TYPE>` | `getTopGroups(int withinGroupOffset)`
`protected abstract AbstractSecondPassGroupingCollector.SearchGroupDocs<GROUP_VALUE_TYPE>` | `retrieveGroup(int doc)` Returns the group the specified doc belongs to or `null` if no group could be retrieved.
`void` | `setNextReader(IndexReader reader, int docBase)` Called before collecting from each IndexReader.
`void` | `setScorer(Scorer scorer)` Called before successive calls to `Collector.collect(int)`.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### groupMap

    protected final Map<GROUP_VALUE_TYPE,AbstractSecondPassGroupingCollector.SearchGroupDocs<GROUP_VALUE_TYPE>> groupMap

### groupDocs

    protected AbstractSecondPassGroupingCollector.SearchGroupDocs<GROUP_VALUE_TYPE>[] groupDocs

Constructor Detail

### AbstractSecondPassGroupingCollector

    public AbstractSecondPassGroupingCollector(Collection<SearchGroup<GROUP_VALUE_TYPE>> groups,
                                               Sort groupSort,
                                               Sort withinGroupSort,
                                               int maxDocsPerGroup,
                                               boolean getScores,
                                               boolean getMaxScores,
                                               boolean fillSortFields)
                                        throws IOException

Throws:
  `IOException`

Method Detail

### setScorer

    public void setScorer(Scorer scorer)
                   throws IOException

  Description copied from class: `Collector`
  Called before successive calls to `Collector.collect(int)`. Implementations that need the score of the current document (passed-in to `Collector.collect(int)`), should save the passed-in Scorer and call scorer.score() when needed.

  Specified by:
    `setScorer` in class `Collector`
  Throws:
    `IOException`

### collect

    public void collect(int doc)
                 throws IOException

  Description copied from class: `Collector`
  Called once for every document matching a query, with the unbased document number.

  Note: This is called in an inner search loop. For good search performance, implementations of this method should not call `Searcher.doc(int)` or `IndexReader.document(int)` on every hit. Doing so can slow searches by an order of magnitude or more.

  Specified by:
    `collect` in class `Collector`
  Throws:
    `IOException`

### retrieveGroup

    protected abstract AbstractSecondPassGroupingCollector.SearchGroupDocs<GROUP_VALUE_TYPE> retrieveGroup(int doc)
                                                                                                    throws IOException

  Returns the group the specified doc belongs to or `null` if no group could be retrieved.

  Parameters:
    `doc` - The specified doc
  Returns:
    the group the specified doc belongs to or `null` if no group could be retrieved
  Throws:
    `IOException` - If an I/O related error occurred

### setNextReader

    public void setNextReader(IndexReader reader,
                              int docBase)
                       throws IOException

  Description copied from class: `Collector`
  Called before collecting from each IndexReader. All doc ids in `Collector.collect(int)` will correspond to reader. Add docBase to the current IndexReaders internal document id to re-base ids in `Collector.collect(int)`.

  Specified by:
    `setNextReader` in class `Collector`
  Parameters:
    `reader` - next IndexReader
  Throws:
    `IOException`

### acceptsDocsOutOfOrder

    public boolean acceptsDocsOutOfOrder()

  Description copied from class: `Collector`
  Return `true` if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) to `Collector.collect(int)`.

  Most Lucene Query implementations will visit matching docIDs in order. However, some queries (currently limited to certain cases of `BooleanQuery`) can achieve faster searching if the `Collector` allows them to deliver the docIDs out of order.

  Many collectors don't mind getting docIDs out of order, so it's important to return `true` here.

  Specified by:
    `acceptsDocsOutOfOrder` in class `Collector`

### getTopGroups

    public TopGroups<GROUP_VALUE_TYPE> getTopGroups(int withinGroupOffset)

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