Package org.apache.lucene.search

Class FieldComparator<T>

    • Constructor Detail

      • FieldComparator

        public FieldComparator()

    • Method Detail

      • compare

        public abstract int compare​(int slot1,
                            int slot2)
        Compare hit at slot1 with hit at slot2.
        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

      • setBottom

        public abstract void setBottom​(int slot)
        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

      • compareBottom

        public abstract 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 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

        public abstract 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 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 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 abstract 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

      • setNextReader

        public abstract FieldComparator<T> setNextReader​(AtomicReaderContext context)
                                          throws IOException
        Set a new AtomicReaderContext. All subsequent docIDs are relative to the current reader (you must add docBase if you need to map it to a top-level docID).
        Parameters:
        context - current reader context
        Returns:
        the comparator to use for this segment; most comparators can just return "this" to reuse the same comparator across segments
        Throws:
        IOException - if there is a low-level IO error

      • setScorer

        public void setScorer​(Scorer scorer)
        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.

      • value

        public abstract T value​(int slot)
        Return the actual value in the slot.
        Parameters:
        slot - the value
        Returns:
        value in this slot

      • compareValues

        public int compareValues​(T first,
                         T second)
        Returns -1 if first is less than second. 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