/**
* @param reader
* @param numTerms
* @param field
* @return TermStats[] ordered by terms with highest docFreq first.
* @throws Exception
*/
public static TermStats[] getHighFreqTerms(IndexReader reader, int numTerms, String[] fieldNames)
throws Exception {
TermStatsQueue tiq = null;
TermsEnum te = null;
if (fieldNames != null) {
Fields fields = MultiFields.getFields(reader);
if (fields == null) {
LOG.info("Index with no fields - probably empty or corrupted");
return EMPTY_STATS;
}
tiq = new TermStatsQueue(numTerms);
for (String field : fieldNames) {
Terms terms = fields.terms(field);
if (terms != null) {
te = terms.iterator(te);
fillQueue(te, tiq, field);
}
}
} else {
Fields fields = MultiFields.getFields(reader);
if (fields == null) {
LOG.info("Index with no fields - probably empty or corrupted");
return EMPTY_STATS;
}
tiq = new TermStatsQueue(numTerms);
Iterator<String> fieldIterator = fields.iterator();
while (fieldIterator.hasNext()) {
String field = fieldIterator.next();
Terms terms = fields.terms(field);
if (terms != null) {
te = terms.iterator(te);
fillQueue(te, tiq, field);
}
}
}
TermStats[] result = new TermStats[tiq.size()];
// we want highest first so we read the queue and populate the array
// starting at the end and work backwards
int count = tiq.size() - 1;
while (tiq.size() != 0) {
result[count] = tiq.pop();
count--;
}
return result;
}
public static void fillQueue(TermsEnum termsEnum, TermStatsQueue tiq, String field)
throws Exception {
BytesRef term;
while ((term = termsEnum.next()) != null) {
BytesRef r = new BytesRef();
r.copyBytes(term);
tiq.insertWithOverflow(new TermStats(field, r, termsEnum.docFreq()));
}
}