org.apache.lucene.search.CollectionStatistics#field ( )源码实例Demo

@Override
   public final SimWeight computeWeight(CollectionStatistics collectionStats,
				 TermStatistics... termStats)
   {
float N, n, idf, adl;
idf = 1.0f;
N   = collectionStats.maxDoc();
adl = collectionStats.sumTotalTermFreq() / N;

if (termStats.length == 1) {
    n = termStats[0].docFreq();
    idf = log(N/n);
}
else {
    for (final TermStatistics stat : termStats) {
	n = stat.docFreq();
	idf += log(N/n);
    }
}

return new TFIDFWeight(collectionStats.field(), idf, adl);
   }
 

public CollectionStats(CollectionStatistics stats) {
  this.field = stats.field();
  this.maxDoc = stats.maxDoc();
  this.docCount = stats.docCount();
  this.sumTotalTermFreq = stats.sumTotalTermFreq();
  this.sumDocFreq = stats.sumDocFreq();
}
 

@Override
public final SimWeight computeWeight(CollectionStatistics collectionStats, TermStatistics... termStats) {
  Explanation idf = termStats.length == 1 ? idfExplain(collectionStats, termStats[0]) : idfExplain(collectionStats, termStats);

  float avgdl = avgFieldLength(collectionStats);

  // compute freq-independent part of bm25 equation across all norm values
  float cache[] = new float[256];
  for (int i = 0; i < cache.length; i++) {
    cache[i] = k1 * ((1 - b) + b * decodeNormValue((byte)i) / avgdl);
  }
  return new BM25Stats(collectionStats.field(), idf, avgdl, cache);
}
 

@Override
   public final SimWeight computeWeight(CollectionStatistics collectionStats,
				 TermStatistics... termStats)
   {
long  N, n;
float idf_, avdl;

idf_ = 1.0f;

N    = collectionStats.docCount();
if (N == -1)
    N = collectionStats.maxDoc();

avdl = collectionStats.sumTotalTermFreq() / N;

if (termStats.length == 1) {
    n    = termStats[0].docFreq();
    idf_ = idf(n, N);
}
else { /* computation for a phrase */
    for (final TermStatistics stat : termStats) {
	n     = stat.docFreq();
	idf_ += idf(n, N);
    }
}

return new TFIDFWeight(collectionStats.field(), idf_, avdl);
   }