问题
I want to serve my users the most relevant and best results. For example, I'm rewarding records that have a big title, description, attached photos, etc. For context: the records are bicycle routes, having routepoints (coordinates) and metadata like photos, reviews, etc.
Now, I have indexed these records using Hibernate and then I search within the index using Lucene in Hibernate Search. To score my results, I build queries based on the document properties and boost them (using boostedTo()) in a should BooleanJunction clause:
bj.should(qb.range().onField("descriptionLength").above(3000).createQuery()).boostedTo(3.0f);
bj.should(qb.range().onField("views.views").above(5000).createQuery()).boostedTo(3.0f);
bj.should(qb.range().onField("nameLength").above(20).createQuery()).boostedTo(1.0f);
bj.should(qb.range().onField("picturesLength").above(0).createQuery()).boostedTo(5.0f);
bj.should(qb.keyword().onField("routePoints.poi.participant").matching("true").createQuery()).boostedTo(10.0f);
To try and disable Lucene's scoring, I have overridden the DefaultSimilarity class, set all the comparing to 1.0f score and enabled it via Hibernate config:
public class IgnoreScoringSimilarity extends DefaultSimilarity {
@Override
public float idf(long docFreq, long numDocs) {
return 1.0f;
}
@Override
public float tf(float freq) {
return 1.0f;
}
@Override
public float coord(int overlap, int maxOverlap) {
return 1.0f;
}
@Override
public float lengthNorm(FieldInvertState state) {
return 1.0f;
}
@Override
public float queryNorm(float sumOfSquaredWeights) {
return 1.0f;
}
}
Hibernate config:
<property name="hibernate.search.default.similarity" value="com.search.IgnoreScoringSimilarity"/>
This approach works for 90% of the time, however, I am still seeing some weird results that seem to be out of place. The pattern I recognize is that these routes (documents) are very large in size. A normal route has about 20-30 routepoints, however these out-of-place results have 100-150. This leaves me to believe that default Lucene scoring is still happening (scoring higher because of document size).
Am I doing something wrong in disabling Lucene's scoring? Could there be another explanation?
回答1:
I can suggest another approach based on custom result sorting. You can read about it in the answer. This answer is a slightly outdated, so I modified this example according to Lucene API 4.10.1. Comparator
public abstract class CustomComparator extends FieldComparator<Double> {
double[] scoring;
double bottom;
double topValue;
private FieldCache.Ints[] currentReaderValues;
private String[] fields;
protected abstract double getScore(int[] value);
public CustomComparator(int hitNum, String[] fields) {
this.fields = fields;
scoring = new double[hitNum];
}
int[] fromReaders(int doc) {
int[] result = new int[currentReaderValues.length];
for (int i = 0; i < result.length; i++) {
result[i] = currentReaderValues[i].get(doc);
}
return result;
}
@Override
public int compare(int slot1, int slot2) {
return Double.compare(scoring[slot1], scoring[slot2]);
}
@Override
public void setBottom(int slot) {
this.bottom = scoring[slot];
}
@Override
public void setTopValue(Double top) {
topValue = top;
}
@Override
public int compareBottom(int doc) throws IOException {
double v2 = getScore(fromReaders(doc));
return Double.compare(bottom, v2);
}
@Override
public int compareTop(int doc) throws IOException {
double docValue = getScore(fromReaders(doc));
return Double.compare(topValue, docValue);
}
@Override
public void copy(int slot, int doc) throws IOException {
scoring[slot] = getScore(fromReaders(doc));
}
@Override
public FieldComparator<Double> setNextReader(AtomicReaderContext atomicReaderContext) throws IOException {
currentReaderValues = new FieldCache.Ints[fields.length];
for (int i = 0; i < fields.length; i++) {
currentReaderValues[i] = FieldCache.DEFAULT.getInts(atomicReaderContext.reader(), fields[i], null, false);
}
return this;
}
@Override
public Double value(int slot) {
return scoring[slot];
}
}
Example of search
public class SortExample {
public static void main(String[] args) throws IOException {
final String[] fields = new String[]{"descriptionLength", "views.views", "nameLength"};
Sort sort = new Sort(
new SortField(
"",
new FieldComparatorSource() {
public FieldComparator newComparator(String fieldname, int numHits, int sortPos, boolean reversed) throws IOException {
return new CustomComparator(numHits, fields) {
@Override
protected double getScore(int[] value) {
int descriptionLength = value[0];
int views = value[1];
int nameLength = value[2];
return -((descriptionLength > 2000.0 ? 5.0 : 0.0) +
(views > 5000.0 ? 3.0 : 0.0) +
(nameLength > 20.0 ? 1.0 : 0.0));
}
};
}
}
)
);
IndexWriterConfig indexWriterConfig = new IndexWriterConfig(Version.LUCENE_4_10_4, new StandardAnalyzer());
Directory directory = new RAMDirectory();
IndexWriter indexWriter = new IndexWriter(directory, indexWriterConfig);
addDoc(indexWriter, "score 0", 1000, 1000, 10);
addDoc(indexWriter, "score 5", 3000, 1000, 10);
addDoc(indexWriter, "score 3", 1000, 6000, 10);
addDoc(indexWriter, "score 1", 1000, 1000, 30);
addDoc(indexWriter, "score 4", 1000, 6000, 30);
addDoc(indexWriter, "score 6", 5000, 1000, 30);
addDoc(indexWriter, "score 9", 5000, 6000, 30);
final IndexReader indexReader = DirectoryReader.open(indexWriter, false);
IndexSearcher indexSearcher = new IndexSearcher(indexReader);
Query query = new TermQuery(new Term("all", "all"));
int nDocs = 100;
final TopDocs search = indexSearcher.search(query, null, nDocs, sort);
System.out.println("Max " + search.scoreDocs.length + " " + search.getMaxScore());
for (ScoreDoc sd : search.scoreDocs) {
Document document = indexReader.document(sd.doc);
System.out.println(document.getField("name").stringValue());
}
}
private static void addDoc(IndexWriter indexWriter, String name, int descriptionLength, int views, int nameLength) throws IOException {
Document doc = new Document();
doc.add(new TextField("name", name, Field.Store.YES));
doc.add(new TextField("all", "all", Field.Store.YES));
doc.add(new IntField("descriptionLength", descriptionLength, Field.Store.YES));
doc.add(new IntField("views.views", views, Field.Store.YES));
doc.add(new IntField("nameLength", nameLength, Field.Store.YES));
indexWriter.addDocument(doc);
}
}
Code will output
score 9
score 6
score 5
score 4
score 3
score 1
score 0
来源：https://stackoverflow.com/questions/30708833/how-to-disable-default-scoring-boosting-in-hibernate-search-lucene