org.apache.lucene.search

## Class FieldComparator.RelevanceComparator

- java.lang.Object
- - org.apache.lucene.search.FieldComparator<Float>
  - - org.apache.lucene.search.FieldComparator.RelevanceComparator

- All Implemented Interfaces:
    LeafFieldComparator
  Enclosing class:
    FieldComparator<T>

      public static final class FieldComparator.RelevanceComparator
      extends FieldComparator<Float>
      implements LeafFieldComparator

  Sorts by descending relevance. NOTE: if you are sorting only by descending relevance and then secondarily by ascending docID, performance is faster using `TopScoreDocCollector` directly (which `IndexSearcher.search(org.apache.lucene.search.Query, int)` uses when no `Sort` is specified).

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class org.apache.lucene.search.FieldComparator

      `FieldComparator.DocComparator, FieldComparator.DoubleComparator, FieldComparator.FloatComparator, FieldComparator.IntComparator, FieldComparator.LongComparator, FieldComparator.NumericComparator<T extends Number>, FieldComparator.RelevanceComparator, FieldComparator.TermOrdValComparator, FieldComparator.TermValComparator`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `RelevanceComparator(int numHits)` Creates a new comparator based on relevance for `numHits`.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `int` | `compare(int slot1, int slot2)` Compare hit at slot1 with hit at slot2.
    `int` | `compareBottom(int doc)` Compare the bottom of the queue with this doc.
    `int` | `compareTop(int doc)` Compare the top value with this doc.
    `int` | `compareValues(Float first, Float second)` Returns a negative integer if first is less than second, 0 if they are equal and a positive integer otherwise.
    `void` | `copy(int slot, int doc)` This method is called when a new hit is competitive.
    `LeafFieldComparator` | `getLeafComparator(LeafReaderContext context)` Get a per-segment `LeafFieldComparator` to collect the given `LeafReaderContext`.
    `void` | `setBottom(int bottom)` Set the bottom slot, ie the "weakest" (sorted last) entry in the queue.
    `void` | `setScorer(Scorable scorer)` Sets the Scorer to use in case a document's score is needed.
    `void` | `setTopValue(Float value)` Record the top value, for future calls to `LeafFieldComparator.compareTop(int)`.
    `Float` | `value(int slot)` Return the actual value in the slot.

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

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

- - ### Constructor Detail

    - #### RelevanceComparator

          public RelevanceComparator(int numHits)

      Creates a new comparator based on relevance for `numHits`.

  - ### Method Detail

    - #### compare

          public int compare(int slot1,
                             int slot2)

      Description copied from class: `FieldComparator`
      Compare hit at slot1 with hit at slot2.
      Specified by:
        `compare` in class `FieldComparator<Float>`
      Parameters:
        `slot1` - first slot to compare
        `slot2` - second slot to compare
      Returns:
        any `N < 0` if slot2's value is sorted after slot1, any `N > 0` if the slot2's value is sorted before slot1 and `0` if they are equal

    - #### compareBottom

          public int compareBottom(int doc)
                            throws IOException

      Description copied from interface: `LeafFieldComparator`
      Compare the bottom of the queue with this doc. This will only invoked after setBottom has been called. This should return the same result as `FieldComparator.compare(int,int)`} as if bottom were slot1 and the new document were slot 2.

      For a search that hits many results, this method will be the hotspot (invoked by far the most frequently).

      Specified by:
        `compareBottom` in interface `LeafFieldComparator`
      Parameters:
        `doc` - that was hit
      Returns:
        any `N < 0` if the doc's value is sorted after the bottom entry (not competitive), any `N > 0` if the doc's value is sorted before the bottom entry and `0` if they are equal.
      Throws:
        `IOException`

    - #### copy

          public void copy(int slot,
                           int doc)
                    throws IOException

      Description copied from interface: `LeafFieldComparator`
      This method is called when a new hit is competitive. You should copy any state associated with this document that will be required for future comparisons, into the specified slot.
      Specified by:
        `copy` in interface `LeafFieldComparator`
      Parameters:
        `slot` - which slot to copy the hit to
        `doc` - docID relative to current reader
      Throws:
        `IOException`

    - #### getLeafComparator

          public LeafFieldComparator getLeafComparator(LeafReaderContext context)

      Description copied from class: `FieldComparator`
      Get a per-segment `LeafFieldComparator` to collect the given `LeafReaderContext`. All docIDs supplied to this `LeafFieldComparator` are relative to the current reader (you must add docBase if you need to map it to a top-level docID).
      Specified by:
        `getLeafComparator` in class `FieldComparator<Float>`
      Parameters:
        `context` - current reader context
      Returns:
        the comparator to use for this segment

    - #### setBottom

          public void setBottom(int bottom)

      Description copied from interface: `LeafFieldComparator`
      Set the bottom slot, ie the "weakest" (sorted last) entry in the queue. When `LeafFieldComparator.compareBottom(int)` is called, you should compare against this slot. This will always be called before `LeafFieldComparator.compareBottom(int)`.
      Specified by:
        `setBottom` in interface `LeafFieldComparator`
      Parameters:
        `bottom` - the currently weakest (sorted last) slot in the queue

    - #### setTopValue

          public void setTopValue(Float value)

      Description copied from class: `FieldComparator`
      Record the top value, for future calls to `LeafFieldComparator.compareTop(int)`. This is only called for searches that use searchAfter (deep paging), and is called before any calls to `FieldComparator.getLeafComparator(LeafReaderContext)`.
      Specified by:
        `setTopValue` in class `FieldComparator<Float>`

    - #### setScorer

          public void setScorer(Scorable scorer)

      Description copied from interface: `LeafFieldComparator`
      Sets the Scorer to use in case a document's score is needed.
      Specified by:
        `setScorer` in interface `LeafFieldComparator`
      Parameters:
        `scorer` - Scorer instance that you should use to obtain the current hit's score, if necessary.

    - #### value

          public Float value(int slot)

      Description copied from class: `FieldComparator`
      Return the actual value in the slot.
      Specified by:
        `value` in class `FieldComparator<Float>`
      Parameters:
        `slot` - the value
      Returns:
        value in this slot

    - #### compareValues

          public int compareValues(Float first,
                                   Float second)

      Description copied from class: `FieldComparator`
      Returns a negative integer if first is less than second, 0 if they are equal and a positive integer otherwise. Default impl to assume the type implements Comparable and invoke .compareTo; be sure to override this method if your FieldComparator's type isn't a Comparable or if your values may sometimes be null
      Overrides:
        `compareValues` in class `FieldComparator<Float>`

    - #### compareTop

          public int compareTop(int doc)
                         throws IOException

      Description copied from interface: `LeafFieldComparator`
      Compare the top value with this doc. This will only invoked after setTopValue has been called. This should return the same result as `FieldComparator.compare(int,int)`} as if topValue were slot1 and the new document were slot 2. This is only called for searches that use searchAfter (deep paging).
      Specified by:
        `compareTop` in interface `LeafFieldComparator`
      Parameters:
        `doc` - that was hit
      Returns:
        any `N < 0` if the doc's value is sorted after the top entry (not competitive), any `N > 0` if the doc's value is sorted before the top entry and `0` if they are equal.
      Throws:
        `IOException`

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