Package org.apache.lucene.search.grouping

# Class GroupSelector<T>

java.lang.Object
org.apache.lucene.search.grouping.GroupSelector<T>

Type Parameters:
  `T` - the type of the group value

Direct Known Subclasses:
  `DoubleRangeGroupSelector`, `LongRangeGroupSelector`, `TermGroupSelector`, `ValueSourceGroupSelector`

public abstract class GroupSelector<T> extends Object
Defines a group, for use by grouping collectors

A GroupSelector acts as an iterator over documents. For each segment, clients should call `setNextReader(LeafReaderContext)`, and then `advanceTo(int)` for each matching document.

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `static enum`
  `GroupSelector.State`
  What to do with the current value

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `GroupSelector()`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `abstract GroupSelector.State`
  `advanceTo(int doc)`
  Advance the GroupSelector's iterator to the given document
  `abstract T`
  `copyValue()`
  `abstract T`
  `currentValue()`
  Get the group value of the current document
  `abstract void`
  `setGroups(Collection<SearchGroup<T>> groups)`
  Set a restriction on the group values returned by this selector
  `abstract void`
  `setNextReader(LeafReaderContext readerContext)`
  Set the LeafReaderContext
  `abstract void`
  `setScorer(Scorable scorer)`
  Set the current Scorer

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### GroupSelector

    public GroupSelector()

- ## Method Details

  - ### setNextReader

    public abstract void setNextReader(LeafReaderContext readerContext) throws IOException
    Set the LeafReaderContext
    Throws:
      `IOException`

  - ### setScorer

    public abstract void setScorer(Scorable scorer) throws IOException
    Set the current Scorer
    Throws:
      `IOException`

  - ### advanceTo

    public abstract GroupSelector.State advanceTo(int doc) throws IOException
    Advance the GroupSelector's iterator to the given document
    Throws:
      `IOException`

  - ### currentValue

    public abstract T currentValue() throws IOException
    Get the group value of the current document

    N.B. this object may be reused, for a persistent version use `copyValue()`

    Throws:
      `IOException`

  - ### copyValue

    public abstract T copyValue() throws IOException
    Returns:
      a copy of the group value of the current document
    Throws:
      `IOException`

  - ### setGroups

    public abstract void setGroups(Collection<SearchGroup<T>> groups)
    Set a restriction on the group values returned by this selector

    If the selector is positioned on a document whose group value is not contained within this set, then `advanceTo(int)` will return `GroupSelector.State.SKIP`

    Parameters:
      `groups` - a set of `SearchGroup` objects to limit selections to