Issue with block join query, full code included.

[Anthony Butcher <an...@gmail.com>]

Hello,  Sorry it's the .NET port, but hopefully someone could advise if I'm
using the API in correct way.  This is originally taken from a stack
overflow question from another user, but I have a very similar data set and
search requirements.

I'm trying to index blog posts and comments in a way which allows returning
the blog post documents where the comment contains some text... the `hits`
variable always seems to be null...

Any help would be appreciated, I will try this in JAVA to see if it's the
port?

Thanks

            var analyzer = new StandardAnalyzer(LuceneVersion.LUCENE_48);
            var config = new IndexWriterConfig(LuceneVersion.LUCENE_48,
analyzer);

config.SetOpenMode(IndexWriterConfig.OpenMode_e.CREATE_OR_APPEND);

            var indexPathBlog = "D:\\Test";
            if (System.IO.Directory.Exists(indexPathBlog))
            {
                System.IO.Directory.Delete(indexPathBlog, true);
            }

            System.IO.Directory.CreateDirectory(indexPathBlog);
            var indexDirectoryBlog = FSDirectory.Open(new
System.IO.DirectoryInfo(indexPathBlog));
            var indexWriterBlog = new IndexWriter(indexDirectoryBlog,
config);

            var one = new List<Document>();
            var two = new List<Document>();

            var blogOne = new Document();
            blogOne.Add(new TextField("Id", "1", Field.Store.YES));
            blogOne.Add(new TextField("BlogContent", "Content of first
blog", Field.Store.YES));
            blogOne.Add(new TextField("Type", "blog", Field.Store.YES));
            blogOne.Add(new TextField("Note", "parent", Field.Store.YES));
            one.Add(blogOne);

            Document commentOne = new Document();
            commentOne.Add(new TextField("BlogId", "1", Field.Store.YES));
            commentOne.Add(new TextField("CommentContent", "I like your
first blog!", Field.Store.YES));
            commentOne.Add(new TextField("Type", "comment",
Field.Store.YES));
            commentOne.Add(new TextField("Note", "child", Field.Store.YES));
            one.Add(commentOne);

            Document blogTwo = new Document();
            blogTwo.Add(new TextField("Id", "2", Field.Store.YES));
            blogTwo.Add(new TextField("BlogContent", "This is the second
blog!", Field.Store.YES));
            blogTwo.Add(new TextField("Type", "blog", Field.Store.YES));
            blogTwo.Add(new TextField("Note", "parent", Field.Store.YES));
            two.Add(blogTwo);

            var commentTwo = new Document();
            commentTwo.Add(new TextField("BlogId", "2", Field.Store.YES));
            commentTwo.Add(new TextField("CommentContent", "Not that
great.", Field.Store.YES));
            commentTwo.Add(new TextField("Type", "comment",
Field.Store.YES));
            commentTwo.Add(new TextField("Note", "child", Field.Store.YES));
            two.Add(commentTwo);

            indexWriterBlog.AddDocuments(one);
            indexWriterBlog.AddDocuments(two);

            indexWriterBlog.Commit();

            var searcher = new
IndexSearcher(DirectoryReader.Open(indexDirectoryBlog));

            Filter parentQuery =
                    new QueryWrapperFilter(
                      new TermQuery(
                        new Term("type", "blog")));

            BooleanQuery childQuery = new BooleanQuery();
            childQuery.Add(new TermQuery(new Term("CommentContent", "I like
your first blog!")), BooleanClause.Occur.MUST);

            var commentJoinQuery = new ToParentBlockJoinQuery(
                childQuery,
                parentQuery,
                ScoreMode.None);

            var c = new ToParentBlockJoinCollector(
                Sort.RELEVANCE, // sort
                10,             // numHits
                false,           // trackScores
                false           // trackMaxScore
                );

            searcher.Search(commentJoinQuery, c);

            int maxDocsPerGroup = 10;
            var hits = c.GetTopGroups(
                commentJoinQuery,
                Sort.INDEXORDER,
                0,   // offset
                maxDocsPerGroup,  // maxDocsPerGroup
                0,   // withinGroupOffset
                true // fillSortFields
              );