Package org.apache.lucene.search

Interface LeafFieldComparator

All Known Implementing Classes:

FieldComparator.DocComparator, FieldComparator.DoubleComparator, FieldComparator.FloatComparator, FieldComparator.IntComparator, FieldComparator.LongComparator, FieldComparator.NumericComparator, FieldComparator.RelevanceComparator, FieldComparator.TermOrdValComparator, FieldComparator.TermValComparator, SimpleFieldComparator

public interface LeafFieldComparator

Expert: comparator that gets instantiated on each leaf from a top-level FieldComparator instance.

A leaf comparator must define these functions:

• setBottom(int) This method is called by FieldValueHitQueue to notify the FieldComparator of the current weakest ("bottom") slot. Note that this slot may not hold the weakest value according to your comparator, in cases where your comparator is not the primary one (ie, is only used to break ties from the comparators before it).
• compareBottom(int) Compare a new hit (docID) against the "weakest" (bottom) entry in the queue.
• compareTop(int) Compare a new hit (docID) against the top value previously set by a call to FieldComparator.setTopValue(T).
• copy(int, int) Installs a new hit into the priority queue. The FieldValueHitQueue calls this method when a new hit is competitive.

See Also:

FieldComparator

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

Method Summary

Modifier and Type	Method	Description
int	compareBottom(int doc)	Compare the bottom of the queue with this doc.
int	compareTop(int doc)	Compare the top value with this doc.
void	copy(int slot, int doc)	This method is called when a new hit is competitive.
void	setBottom(int slot)	Set the bottom slot, ie the "weakest" (sorted last) entry in the queue.
void	setScorer(Scorer scorer)	Sets the Scorer to use in case a document's score is needed.

Method Detail

setBottom

void setBottom(int slot)
        throws IOException

Set the bottom slot, ie the "weakest" (sorted last) entry in the queue. When compareBottom(int) is called, you should compare against this slot. This will always be called before compareBottom(int).

Parameters:

slot - the currently weakest (sorted last) slot in the queue

Throws:

IOException

compareBottom

int compareBottom(int doc)
           throws IOException

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).

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

compareTop

int compareTop(int doc)
        throws IOException

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).

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

copy

void copy(int slot,
          int doc)
   throws IOException

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.

Parameters:

slot - which slot to copy the hit to

doc - docID relative to current reader

Throws:

IOException

setScorer

void setScorer(Scorer scorer)
        throws IOException

Sets the Scorer to use in case a document's score is needed.

Parameters:

scorer - Scorer instance that you should use to obtain the current hit's score, if necessary.

Throws:

IOException