/// <summary>
/// Returns the <see cref="PassageScorer"/> to use for
/// ranking passages. This
/// returns a new <see cref="PassageScorer"/> by default;
/// subclasses can override to customize.
/// </summary>
protected virtual PassageScorer GetScorer(string field)
{
if (defaultScorer is null)
{
defaultScorer = new PassageScorer();
}
return(defaultScorer);
}
// algorithm: treat sentence snippets as miniature documents
// we can intersect these with the postings lists via BreakIterator.preceding(offset),s
// score each sentence as norm(sentenceStartOffset) * sum(weight * tf(freq))
private Passage[] HighlightDoc(string field, BytesRef[] terms, int contentLength, BreakIterator bi, int doc,
TermsEnum termsEnum, DocsAndPositionsEnum[] postings, int n)
{
PassageScorer scorer = GetScorer(field);
if (scorer is null)
{
// LUCENENET: Changed from NullPointerException to InvalidOperationException (which isn't caught anywhere outside of tests)
throw IllegalStateException.Create("PassageScorer cannot be null");
}
JCG.PriorityQueue <OffsetsEnum> pq = new JCG.PriorityQueue <OffsetsEnum>();
float[] weights = new float[terms.Length];
// initialize postings
for (int i = 0; i < terms.Length; i++)
{
DocsAndPositionsEnum de = postings[i];
int pDoc;
if (de == EMPTY)
{
continue;
}
else if (de is null)
{
postings[i] = EMPTY; // initially
if (!termsEnum.SeekExact(terms[i]))
{
continue; // term not found
}
de = postings[i] = termsEnum.DocsAndPositions(null, null, DocsAndPositionsFlags.OFFSETS);
if (de is null)
{
// no positions available
throw new ArgumentException("field '" + field + "' was indexed without offsets, cannot highlight");
}
pDoc = de.Advance(doc);
}
else
{
pDoc = de.DocID;
if (pDoc < doc)
{
pDoc = de.Advance(doc);
}
}
if (doc == pDoc)
{
weights[i] = scorer.Weight(contentLength, de.Freq);
de.NextPosition();
pq.Add(new OffsetsEnum(de, i));
}
}
pq.Add(new OffsetsEnum(EMPTY, int.MaxValue)); // a sentinel for termination
JCG.PriorityQueue <Passage> passageQueue = new JCG.PriorityQueue <Passage>(n, Comparer <Passage> .Create((left, right) =>
{
if (left.score < right.score)
{
return(-1);
}
else if (left.score > right.score)
{
return(1);
}
else
{
return(left.startOffset - right.startOffset);
}
}));
Passage current = new Passage();
while (pq.TryDequeue(out OffsetsEnum off))
{
DocsAndPositionsEnum dp = off.dp;
int start = dp.StartOffset;
if (start == -1)
{
throw new ArgumentException("field '" + field + "' was indexed without offsets, cannot highlight");
}
int end = dp.EndOffset;
// LUCENE-5166: this hit would span the content limit... however more valid
// hits may exist (they are sorted by start). so we pretend like we never
// saw this term, it won't cause a passage to be added to passageQueue or anything.
if (Debugging.AssertsEnabled)
{
Debugging.Assert(EMPTY.StartOffset == int.MaxValue);
}
if (start < contentLength && end > contentLength)
{
continue;
}
if (start >= current.endOffset)
{
if (current.startOffset >= 0)
{
// finalize current
current.score *= scorer.Norm(current.startOffset);
// new sentence: first add 'current' to queue
if (passageQueue.Count == n && current.score < passageQueue.Peek().score)
{
current.Reset(); // can't compete, just reset it
}
else
{
passageQueue.Enqueue(current);
if (passageQueue.Count > n)
{
current = passageQueue.Dequeue();
current.Reset();
}
else
{
current = new Passage();
}
}
}
// if we exceed limit, we are done
if (start >= contentLength)
{
Passage[] passages = passageQueue.ToArray();
foreach (Passage p in passages)
{
p.Sort();
}
// sort in ascending order
ArrayUtil.TimSort(passages, Comparer <Passage> .Create((left, right) => left.startOffset - right.startOffset));
return(passages);
}
// advance breakiterator
if (Debugging.AssertsEnabled)
{
Debugging.Assert(BreakIterator.Done < 0);
}
current.startOffset = Math.Max(bi.Preceding(start + 1), 0);
current.endOffset = Math.Min(bi.Next(), contentLength);
}
int tf = 0;
while (true)
{
tf++;
BytesRef term = terms[off.id];
if (term is null)
{
// multitermquery match, pull from payload
term = off.dp.GetPayload();
if (Debugging.AssertsEnabled)
{
Debugging.Assert(term != null);
}
}
current.AddMatch(start, end, term);
if (off.pos == dp.Freq)
{
break; // removed from pq
}
else
{
off.pos++;
dp.NextPosition();
start = dp.StartOffset;
end = dp.EndOffset;
}
if (start >= current.endOffset || end > contentLength)
{
pq.Enqueue(off);
break;
}
}
current.score += weights[off.id] * scorer.Tf(tf, current.endOffset - current.startOffset);
}
// Dead code but compiler disagrees:
if (Debugging.AssertsEnabled)
{
Debugging.Assert(false);
}
return(null);
}
