org.apache.lucene.search.grouping
Class AbstractFirstPassGroupingCollector<GROUP_VALUE_TYPE>

java.lang.Object
  extended by org.apache.lucene.search.Collector
      extended by org.apache.lucene.search.grouping.AbstractFirstPassGroupingCollector<GROUP_VALUE_TYPE>
Direct Known Subclasses:
FunctionFirstPassGroupingCollector, TermFirstPassGroupingCollector

public abstract class AbstractFirstPassGroupingCollector<GROUP_VALUE_TYPE>
extends Collector

FirstPassGroupingCollector is the first of two passes necessary to collect grouped hits. This pass gathers the top N sorted groups. 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.

Field Summary
protected  TreeSet<CollectedSearchGroup<GROUP_VALUE_TYPE>> orderedGroups
           
 
Constructor Summary
AbstractFirstPassGroupingCollector(Sort groupSort, int topNGroups)
          Create the first pass collector.
 
Method Summary
 boolean acceptsDocsOutOfOrder()
           
 void collect(int doc)
           
protected abstract  GROUP_VALUE_TYPE copyDocGroupValue(GROUP_VALUE_TYPE groupValue, GROUP_VALUE_TYPE reuse)
          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.
protected abstract  GROUP_VALUE_TYPE getDocGroupValue(int doc)
          Returns the group value for the specified doc.
 Collection<SearchGroup<GROUP_VALUE_TYPE>> getTopGroups(int groupOffset, boolean fillFields)
          Returns top groups, starting from offset.
 void setNextReader(AtomicReaderContext readerContext)
           
 void setScorer(Scorer scorer)
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

orderedGroups

protected TreeSet<CollectedSearchGroup<GROUP_VALUE_TYPE>> orderedGroups
NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
Constructor Detail

AbstractFirstPassGroupingCollector

public AbstractFirstPassGroupingCollector(Sort groupSort,
                                          int topNGroups)
                                   throws IOException
Create the first pass collector.

Parameters:
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 - If I/O related errors occur
Method Detail

getTopGroups

public Collection<SearchGroup<GROUP_VALUE_TYPE>> getTopGroups(int groupOffset,
                                                              boolean fillFields)
Returns top groups, starting from offset. This may return null, if no groups were collected, or if the number of unique groups collected is <= offset.

Parameters:
groupOffset - The offset in the collected groups
fillFields - Whether to fill to SearchGroup.sortValues
Returns:
top groups, starting from offset

setScorer

public void setScorer(Scorer scorer)
               throws IOException
Specified by:
setScorer in class Collector
Throws:
IOException

collect

public void collect(int doc)
             throws IOException
Specified by:
collect in class Collector
Throws:
IOException

acceptsDocsOutOfOrder

public boolean acceptsDocsOutOfOrder()
Specified by:
acceptsDocsOutOfOrder in class Collector

setNextReader

public void setNextReader(AtomicReaderContext readerContext)
                   throws IOException
Specified by:
setNextReader in class Collector
Throws:
IOException

getDocGroupValue

protected abstract GROUP_VALUE_TYPE getDocGroupValue(int doc)
Returns the group value for the specified doc.

Parameters:
doc - The specified doc
Returns:
the group value for the specified doc

copyDocGroupValue

protected abstract GROUP_VALUE_TYPE copyDocGroupValue(GROUP_VALUE_TYPE groupValue,
                                                      GROUP_VALUE_TYPE reuse)
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.

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


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