RavenDB ID for child documents

Question

I like how cleanly an object is stored in ravenDB, but have a practical question for which I'm not sure of the best answer.

Lets say i have a quote request:

QuoteRequest.cs

int Id;
dateTime DateCreated;
List<Quotes> Quotes;

Quote.cs

int ProviderId;
int Price;
int ServiceDays;
int ServiceTypeId;

when someone hits a page, i spit out a list of quotes from which they can choose. These quotes are only related to an instance of the quote request.

My question is, since a child object, such as a quote in the list, doesnt have an Id generated by the database, how do I generate a querystring to let the next page know which quote the user wants to buy?

There could be multiple quotes by one providerId.

My thoughts were either add a QuoteId and increment it based on this.Quotes.Count, but that seems a little hacky, or generate a random number, also a little hacky.

How do people generally handle something like this?

Answer 1

Do you really need to associate the purchase (what the user chose to buy) with the original quote? I'm guessing that you take the quote and then convert it to a purchase. If that is so, then don't worry about an id at all. Just pass along the constituent values to the next step. In other words, treat quote like a Value in the DDD sense.

However, if you do need to store an association to the purchase... well, then it depends on what you really need to track. For example, you could just update the QuoteRequest, marking the selected quote. (Add an IsSelected or something similar to the quote class Quote.) Then the purchase could be linked back to the quote request, and you could identify the quote by way of the flags.

Again, all this depends on the context (and I'm just making guesses about that).

Answer 2

Since no one has answered this yet I'll just say how I would do it;

Why add a Id at all? just use the index of the List? It the request is "?quote=0" they get the quote at position 0?

Not really sure If I'm not getting something here though...

Answer 3

One option is to have the parent object store the last used id. When adding a new child object you increment the id-counter and add that to the child. When the object is saved the id-counter is automatically incremented.

Lets say you have blog post with comments:

public class Post
{
  public int NextCommentId;
  public List<Comment> Comments;
  ...
}

...

var comment = new Comment { Id = post.NextCommentId++ };
post.Comments.Add(comment);

session.SaveChanges();

The code above might not be 100% correct, but should give you an idea of how to do it at least!