/// <summary>
/// Compute the union of the provided sets. This method is much faster than
/// computing the union manually since it operates directly at the byte level.
/// </summary>
public static WAH8DocIdSet Union(ICollection <WAH8DocIdSet> docIdSets, int indexInterval)
{
switch (docIdSets.Count)
{
case 0:
return(EMPTY);
case 1:
return(docIdSets.First());
}
// The logic below is very similar to DisjunctionScorer
int numSets = docIdSets.Count;
PriorityQueue <Iterator> iterators = new PriorityQueueAnonymousInnerClassHelper(numSets);
foreach (WAH8DocIdSet set in docIdSets)
{
Iterator iterator = (Iterator)set.GetIterator();
iterator.NextWord();
iterators.Add(iterator);
}
Iterator top = iterators.Top;
if (top.wordNum == int.MaxValue)
{
return(EMPTY);
}
int wordNum = top.wordNum;
byte word = top.word;
WordBuilder builder = (WordBuilder)(new WordBuilder()).SetIndexInterval(indexInterval);
while (true)
{
top.NextWord();
iterators.UpdateTop();
top = iterators.Top;
if (top.wordNum == wordNum)
{
word |= top.word;
}
else
{
builder.AddWord(wordNum, word);
if (top.wordNum == int.MaxValue)
{
break;
}
wordNum = top.wordNum;
word = top.word;
}
}
return(builder.Build());
}
