maxFreq = 0;
AdaptiveHistogram hist = new AdaptiveHistogram();
termEnum = reader.terms(new Term(field,""));
while (termEnum.next()) {
hist.addValue(termEnum.docFreq());
terms++;
maxFreq = Math.max(maxFreq,termEnum.docFreq());
}
threshold = (int)hist.getValueForPercentile(90);