Review

Iterator.next() is invoked without prior check that the iterator has more elements. There is a second iterator who is checked and is apparently assumed to have as many elements. However, this is not ensured within the method.

• missing/condition/value_or_state

org/apache/lucene/search/BooleanQuery.java

scorer(IndexReader, boolean, boolean)

class BooleanQuery.BooleanWeight {
    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer)
        throws IOException {
      List required = new ArrayList();
      List prohibited = new ArrayList();
      List optional = new ArrayList();
      for (Iterator wIter = weights.iterator(), cIter = clauses.iterator(); wIter.hasNext();) {
        Weight w = (Weight) wIter.next();
        BooleanClause c = (BooleanClause) cIter.next();
        Scorer subScorer = w.scorer(reader, true, false);
        if (subScorer == null) {
          if (c.isRequired()) {
            return null;
          }
        } else if (c.isRequired()) {
          required.add(subScorer);
        } else if (c.isProhibited()) {
          prohibited.add(subScorer);
        } else {
          optional.add(subScorer);
        }
      }
      
      // Check if we can return a BooleanScorer
      scoreDocsInOrder |= !allowDocsOutOfOrder; // until it is removed, factor in the static setting.
      if (!scoreDocsInOrder && topScorer && required.size() == 0 && prohibited.size() < 32) {
        return new BooleanScorer(similarity, minNrShouldMatch, optional, prohibited);
      }
      
      if (required.size() == 0 && optional.size() == 0) {
        // no required and optional clauses.
        return null;
      } else if (optional.size() < minNrShouldMatch) {
        // either >1 req scorer, or there are 0 req scorers and at least 1
        // optional scorer. Therefore if there are not enough optional scorers
        // no documents will be matched by the query
        return null;
      }
      
      // Return a BooleanScorer2
      return new BooleanScorer2(similarity, minNrShouldMatch, required, prohibited, optional);
    }
}