GroupSelector (Lucene 8.5.1 API)

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

Type Parameters:

T - the type of the group value

Direct Known Subclasses:

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 class GroupSelector.State
What to do with the current value

Constructor Summary

Constructors
Constructor Description

GroupSelector()

Method Summary

All Methods Instance Methods Abstract Methods
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 N.B.
`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`
`abstract void`	`setNextReader(LeafReaderContext readerContext)`	Set the LeafReaderContext

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

- Constructor Detail
  - GroupSelector
```
public GroupSelector()
```
- Method Detail
  - setNextReader
```
public abstract void setNextReader(LeafReaderContext readerContext)
                            throws IOException
```
    Set the LeafReaderContext
    
    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()
```
    Get the group value of the current document N.B. this object may be reused, for a persistent version use copyValue()
  - copyValue
```
public abstract T copyValue()
```
    Returns:
    
    a copy of the group value of the current document
  - 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