@Override
public Explanation explain(AtomicReaderContext context, int doc) throws IOException {
ComplexExplanation result = new ComplexExplanation();
result.setDescription("weight(" + getQuery() + " in " + doc + "), product of:");
Explanation idfExpl = new Explanation(idf, "idf(" + field + ":" + idfExp.explain() + ")");
// explain query weight
Explanation queryExpl = new Explanation();
queryExpl.setDescription("queryWeight(" + getQuery() + "), product of:");
Explanation boostExpl = new Explanation(getBoost(), "boost");
if (getBoost() != 1.0f) queryExpl.addDetail(boostExpl);
queryExpl.addDetail(idfExpl);
Explanation queryNormExpl = new Explanation(queryNorm, "queryNorm");
queryExpl.addDetail(queryNormExpl);
queryExpl.setValue(boostExpl.getValue() * idfExpl.getValue() * queryNormExpl.getValue());
result.addDetail(queryExpl);
// explain field weight
ComplexExplanation fieldExpl = new ComplexExplanation();
fieldExpl.setDescription("fieldWeight(" + getQuery() + " in " + doc + "), product of:");
Scorer scorer = scorer(context, ScorerContext.def());
if (scorer == null) {
return new Explanation(0.0f, "no matching docs");
}
Explanation tfExplanation = new Explanation();
int d = scorer.advance(doc);
float phraseFreq;
if (d == doc) {
phraseFreq = scorer.freq();
} else {
phraseFreq = 0.0f;
}
tfExplanation.setValue(similarity.tf(phraseFreq));
tfExplanation.setDescription("tf(phraseFreq=" + phraseFreq + ")");
fieldExpl.addDetail(tfExplanation);
fieldExpl.addDetail(idfExpl);
Explanation fieldNormExpl = new Explanation();
byte[] fieldNorms = context.reader.norms(field);
float fieldNorm = fieldNorms != null ? similarity.decodeNormValue(fieldNorms[doc]) : 1.0f;
fieldNormExpl.setValue(fieldNorm);
fieldNormExpl.setDescription("fieldNorm(field=" + field + ", doc=" + doc + ")");
fieldExpl.addDetail(fieldNormExpl);
fieldExpl.setMatch(Boolean.valueOf(tfExplanation.isMatch()));
fieldExpl.setValue(tfExplanation.getValue() * idfExpl.getValue() * fieldNormExpl.getValue());
result.addDetail(fieldExpl);
result.setMatch(fieldExpl.getMatch());
// combine them
result.setValue(queryExpl.getValue() * fieldExpl.getValue());
if (queryExpl.getValue() == 1.0f) return fieldExpl;
return result;
}