void onSequenceEnd(int j) {
        int sequenceTail = source.getField().terms().size() - j - 1;
        if (tail ==-1 || sequenceTail < tail)
            tail = sequenceTail;

        if (currentSequence > longestSequence)
            longestSequence = currentSequence;
        currentSequence = 0;
    }
Called once per sequence when the sequence ends
searchlib/src/main/java/com/yahoo/searchlib/ranking/features/fieldmatch/FieldMatchMetrics.java