Re: [RavenDB] Data Model & its queries questions

[Oren Eini (Ayende Rahien)]

1) I don't understand the question.

2) If you have session.Advanced.UseOptimisticConcurrency = true; it will throw a concurrency exception, otherwise, last write wins.

3) It uses http mechanism and 304 to detect that.

On Tue, Jul 17, 2012 at 12:31 PM, Mohammad Habbab <moh.h...@gmail.com> wrote:

Since this is my first time writing Raven Database code, i wanted to make sure that my model isn't messing things up and my queries are possible and Valid.Here's my model ( It's a CMS project designed for weird-customer needs -_-  )

class DenormalizedUserInfo

{

    public string EmailAddress {get;set;}

    public string FirstName {get;set;}

    public string LastName {get;set;}

}

class Comment

{

    public string Id {get;set;}

    public string Url {get;set;}

    public string Content {get;set;}

    public DateTime CreationTime {get;set;}

    public DenormalizedUserInfo UserInfo{get;set;}

    public int LikesCount {get;set;}

    public int DisLikesCount {get;set;} 

}

class CommentCollection

{

     public string Url {get;set;}

     public SortedSet<Comment> Comments {get;set;}

}

class Post 

{

    public string Id {get;set;}

    public string Url {get;set;}

    public string Content {get;set;}

    public DateTime CreationTime {get;set;}

    public DenormalizedUserInfo UserInfo {get;set;}

    public int LikesCount {get;set;}

    public int DisLikeCount {get;set;}

    public SortedSet<Comments> RelatedComments {get;set;}

}

The user usecases are: 1- add/remove/modify posts (according to ID). 2- Add/remove/like/dislike comment on a Post (according to [PostID,CommentID] pair).

3-Add/remove/like/dislike comment on a CommentCollection (according to (Url,CommentID) pairs).

I was able to create Indexing classes for: getting a post by Id, post by URL, post by user, commentcollection by Url.

Hah ... that was alot of talk (sorry for talking so long) .. anyway .. my concerns are :

1- In usecases (2) i have to have two pieces of information (namely, postId and CommentId) inorder to get the right object. is there a way to get it using only CommentId by indexing and querying on commentId somehow ? This also applies to usecase (3).

2- Access to my data objects is multi-threaded. Do i need some locking mechanism for my fields when they're modified by multiple threads at the same time (say, two users wanted to add a comment to a post at the same time), or does raven handle this by itself? if so, then how !?

3- I'm using Raven Server over Http (because you recommended this for production). I've read that it provides caching of objects in memory. How does raven alter this cache when i modify a document that is currently in cache ?

 

Thanx .. 

[Mohammad Habbab]

don't mind question (1), I found similar issue u answered on another thread .. thank you.

But about (2) .. does "last write wins" means that if user (A) requested a Post Document and Added a comment (Ac1), and mean while user (B) also requested the same post document and Added a comment (Bc1). then the one who last commits between them is the one who'll have his comment Added, while the other will be overwritten ? If that's the case ... how can i overcome this in my code? Is there some locking mechanism or API i can utilize ?

Cheers !

[Mohammad Habbab]

[Kijana Woodard]

You can Patch ( http://ravendb.net/docs/client-api/partial-document-updates ) values into the comments list or you can keep the comments as their own independent documents without the list in post. Either way will mitigate concurrency issues.

[Oren Eini (Ayende Rahien)]

 If you have session.Advanced.UseOptimisticConcurrency = true; it will throw a concurrency exception 

Ore you can use patching.

[Mohammad Habbab]

Ok .. great .. sounds like patching is very suitable ( specially with the blog example :) )  thank you for the help !