IndexOrDocValuesQuery is counted twice when computing `maxClauseCount`

[iverase]

I noticed that if I change a query from a PointRangeQuery to an IndexOrDocValuesQuery, then the change might make previous valid boolean queries to fail because IndexOrDocValuesQuery counts twice when computing maxClauseCount.

I think this is wrong as IndexOrDocValues is just providing lucene with the choice of two execution paths and should not count twice for that limit.

This test proves the issue:

 public void testIndexOrDocValues() throws IOException {
    Directory dir = newDirectory();
    RandomIndexWriter writer = new RandomIndexWriter(random(), dir);
    Document d = new Document();
    d.add(new LongField("foo", 0L, LongField.Store.NO));
    writer.addDocument(d);
    d = new Document();
    d.add(new LongField("foo", Long.MAX_VALUE, LongField.Store.NO));
    writer.addDocument(d);

    IndexReader reader = writer.getReader();
    IndexSearcher searcher = newSearcher(reader);
    writer.close();
    int maxClauseCount = IndexSearcher.getMaxClauseCount();
    BooleanQuery.Builder qb = new BooleanQuery.Builder();

    for (int i = 0; i < maxClauseCount; i++) {
      qb.add(LongPoint.newRangeQuery("foo", 0, i), BooleanClause.Occur.SHOULD);
    }
    // should not throw an exception, because  it is below the limit
    searcher.rewrite(qb.build());

    qb = new BooleanQuery.Builder();
    for (int i = 0; i < maxClauseCount; i++) {
      qb.add(LongField.newRangeQuery("foo", 0, i), BooleanClause.Occur.SHOULD);
    }
    // should not throw an exception, because  it is below the limit
    searcher.rewrite(qb.build());

    reader.close();
    dir.close();
  }

It fails in the second rewrite with the exception:

org.apache.lucene.search.IndexSearcher$TooManyNestedClauses: Query contains too many nested clauses; maxClauseCount is set to 1024
	at __randomizedtesting.SeedInfo.seed([1DBE2F81F126780A:AB3F95EEC9898FF7]:0)
	at org.apache.lucene.search.IndexSearcher$1.visitLeaf(IndexSearcher.java:905)
	at org.apache.lucene.document.SortedNumericDocValuesRangeQuery.visit(SortedNumericDocValuesRangeQuery.java:74)
	at org.apache.lucene.search.IndexOrDocValuesQuery.visit(IndexOrDocValuesQuery.java:134)
	at org.apache.lucene.search.BooleanQuery.visit(BooleanQuery.java:661)

[iverase]

It is actually even worst in the example I have given. LongField generates an IndexSortSortedNumericDocValuesRangeQuery which will contain the IndexOrDocValuesQuery as a fallback query. it is counting three times each query!