How to use Raven LoadDocument - ravendb

Question

I'm having trouble querying RavenDB with even the simplest of queries, probably I'm doing something wrong, but after a few hours I just can't see it anymore. I've googled almost anything I can think of..
I have these entities:
public class User
{
public string Id { get; set; }
public string DisplayName { get; set; }
public string RealName { get; set; }
public string Email { get; set; }
public string PictureUri { get; set; }
public List<Comment> Comments { get; set; }
public List<Role> Roles { get; set; }
}
public class NewsItem
{
public string Id { get; set; }
public string Title { get; set; }
public string Text { get; set; }
public DateTime Created { get; set; }
public string UserId { get; set; }
public List<Tag> Tags { get; set; }
public List<Comment> Comments { get; set; }
public List<WebImage> Images { get; set; }
}
I want to query these so I get a list of newsItems, but with the user information alongside it. So I read the docs and tried the LoadDocument feature, the index:
public class NewsItemIndexWithComments : AbstractIndexCreationTask<NewsItem, NewsItemIndexWithComments.Result>
{
public class Result
{
public string AuthorName { get; set; }
}
public NewsItemIndexWithComments()
{
Map = newsItems => from newsItem in newsItems
select new
{
AuthorName = LoadDocument<User>(newsItem.UserId).DisplayName
};
}
}
Which I try to use like:
var result = _documentSession.Query<NewsItemIndexWithComments.Result, NewsItemIndexWithComments>().AsProjection<NewsItemIndexWithComments.Result>().ToList();
Now I get the number of documents in my list, but the AuthorName is always null. If I don't use the AsProjection method, I won't get any results. Can anyone show me a proper example on which I can experiment further?
Thanks.
_ edit:
That helped a lot, thanks :) Now for step two, I'm sorry if I'm being a bit newbish, but you'll have to start somewhere. In the newsitems there are comments, in these comments there is another reference to the userid. You can probably guess what I want to do: I want the user info for the comments with the comments as well.
new Index:
public class NewsItemIndexWithComments : AbstractIndexCreationTask<NewsItem, NewsItemIndexWithComments.Result>
{
public class Result : NewsItem
{
public string AuthorName { get; set; }
public string AuthorId { get; set; }
}
public NewsItemIndexWithComments()
{
Map = newsItems => from newsItem in newsItems
let user = LoadDocument<User>(newsItem.UserId)
select new
{
AuthorName = user.DisplayName,
AuthorId = user.Id,
};
Store(x => x.AuthorName, FieldStorage.Yes);
Store(x => x.AuthorId, FieldStorage.Yes);
}
}
Comment class:
public class Comment
{
public string Id { get; set; }
public string Text { get; set; }
public string UserId { get; set; }
public string User { get; set; }
public DateTime Created { get; set; }
}
How can I query the comments and expand the results for that? Or is it better to create a new index just for the comments and get the user info analog to the solution above?

Answer 1

You're almost there, you just need to store the field you are projecting. Add this to the index constructor, after the map.
Store(x=> x.AuthorName, FieldStorage.Yes);
This is because you want it returned and available for AsProjection to find. If you just wanted to use the author name in a where or orderby, you wouldn't need it.

Answer 2

If you just want to include the comments in your AsProjection, you can simply index the entire object along.
Note that indexing a custom object will mean that you're not able to query on it using a .Where(). RavenDB can only query on flattened results (ints, decimals, strings, dates).
In order to, for instance, query on the title, you will need to create a seperate Property public string Title { get; set; } and map it with Title = newsItem.Title.
public class NewsItemIndexWithComments : AbstractIndexCreationTask<NewsItem, NewsItemIndexWithComments.Result>
{
public class Result : NewsItem
{
public string AuthorName { get; set; }
public string AuthorId { get; set; }
public List<Comment> Comments { get; set; }
}
public NewsItemIndexWithComments()
{
Map = newsItems => from newsItem in newsItems
let user = LoadDocument<User>(newsItem.UserId)
select new
{
AuthorName = user.DisplayName,
AuthorId = user.Id,
Comments = newsItem.Comments.
};
Store(x => x.AuthorName, FieldStorage.Yes);
Store(x => x.AuthorId, FieldStorage.Yes);
Store(x => x.Comments, FieldStorage.Yes);
}
}