Ayende @ Rahien

Ayende Rahien commented on NHibernate: Streaming large result sets

Mon, 16 Aug 2010 15:31:08 GMT

Thilo, There are several factors at play here. a) you may be using an ADO.Net provider that will only push results to NHibernate after a significant amount has been reached. b) you may be using a buffered output. The value of streaming is reducing the time to first byte, and you need to ensure that you deal with this in both ends.

Thilo R commented on NHibernate: Streaming large result sets

Mon, 16 Aug 2010 14:48:10 GMT

I tried this approach while streaming a few MBs over UMTS - it takes over 55 seconds. Unfortunately no performance impact was measureable. It seems that the streaming starts as soon as all the data was loaded from the database. Is there something I am missing or is this method not working when streaming from the database directly row by row (like the DataReader)?

Ayende Rahien commented on NHibernate: Streaming large result sets

Fri, 23 Jul 2010 07:18:35 GMT

Bahador , No

Bahador Nooraei B. commented on NHibernate: Streaming large result sets

Thu, 22 Jul 2010 19:14:53 GMT

Is there a nice way to terminate data fetching when we use this approach? I mean, say, we need 100 objects that meet a criteria that can only be enforced in-memory.

Ayende Rahien commented on NHibernate: Streaming large result sets

Thu, 22 Jul 2010 16:58:41 GMT

> the behavior is the same Not really, no. Sure, on the surface it looks like that is all it is doing, but they produce quite a different behavior.

Frank commented on NHibernate: Streaming large result sets

Thu, 22 Jul 2010 15:57:33 GMT

I guess the folks who did the NHibernate.Linq thought otherwise. Whether or not you're reading data from ISession or IStatelessSession, the behavior is the same, it's just one does not do any tracking and the when the foundation is not designed properly, we start seeing things like Linq not working on IStatelessSession. I guess we can agree to disagree but I thank you for your input.

Ayende Rahien commented on NHibernate: Streaming large result sets

Thu, 22 Jul 2010 07:08:26 GMT

@Frank, The problem is that there really aren't is-a between stateless and regular session. They serve different purposes.

Frank commented on NHibernate: Streaming large result sets

Wed, 21 Jul 2010 16:27:10 GMT

So what are your suggestions or pointers? To me, it doesn't make sense to have IStatelessSession and ISession not inherit from some other common interface and I believe there's already a suggested patch (NH-2211) which doesn't look like it made it into the trunk (3.0).

Ayende Rahien commented on NHibernate: Streaming large result sets

Tue, 20 Jul 2010 11:10:20 GMT

@Frank, Probably, but I don't really like that attempt anyway

Frank commented on NHibernate: Streaming large result sets

Mon, 19 Jul 2010 04:01:55 GMT

Doesn't this break NHibernate.Linq which only work under ISession and In essence breaks people's generic repository pattern?

Ayende Rahien commented on NHibernate: Streaming large result sets

Wed, 07 Jul 2010 13:34:05 GMT

Yes

Nabil commented on NHibernate: Streaming large result sets

Wed, 07 Jul 2010 10:22:57 GMT

Does this work with Crtieria API?

Ayende Rahien commented on NHibernate: Streaming large result sets

Wed, 30 Jun 2010 06:36:53 GMT

Ajai, The use of NDataReader depends on the exact mix of what you are doing, the driver that you use and the configuration option. Yes, if it is wrapped, it isn't good, but it is controllable.

Hendry Luk commented on NHibernate: Streaming large result sets

Wed, 30 Jun 2010 03:38:30 GMT

Not to mention that if we use Rx (instead of reinventing another ActionableList), we'll also get all the nice works those guys have been working hard on at Redmond, e.g. Linq support, parallelism. Hence.. // not only caters for simplest use-cases IObservable books = s.CreateQuery("from Book") .Stream(); //Extension method? books.Subscribe(book=> Console.Writeline(book.Name)); // but also fancy stuff IObservable customers = s.CreateQuery("from Customer").Stream(); var mayLike = from book in books join cus in customers on book.Genre == cus.FavouriteGenre select new {Book = book, Customer = cus}; mayLike.Subscribe(x=> Console.WriteLine("Customer {0} may like {1}", x.Book.Title, x.Customer.FullName)}; Maybe a bad example, but thats beside the point. I thought it's a really neat abstraction for a "push-model queryable cursor" :)

Hendry Luk commented on NHibernate: Streaming large result sets

Wed, 30 Jun 2010 02:21:43 GMT

This is precisely what Rx is for. When you created that ActionableList, you actually just reinvented a push-model (akin to IObservable in Rx). I for one would be interested to see Rx (and other .net features) getting built into NH that would enrich it from its java ancestry

Ajai Shankar commented on NHibernate: Streaming large result sets

Tue, 29 Jun 2010 22:23:11 GMT

Hi Ayende Is that really true? I remember quite some while back I wanted to stream results and posting to nhusers made it seem that was not the case: [groups.google.com/.../d9423d9a45ff9c62](http://groups.google.com/group/nhusers/browse_thread/thread/d6da011ed639cb5b/d9423d9a45ff9c62) One of the findings in that thread was: The SqlDataReader is wrapped in a Driver.NDataReader which loads everything into an internal list! Maybe like you said all that was missing is the correct extension point? Ajai

NC commented on NHibernate: Streaming large result sets

Tue, 29 Jun 2010 21:33:18 GMT

Wheres NH3! Heard no news about NH in ages.

Alexey Romanov commented on NHibernate: Streaming large result sets

Tue, 29 Jun 2010 20:12:25 GMT

On one hand I want to say: "That violates semantics of IList completely!" On the other, I don't see a better solution.

Steve Py commented on NHibernate: Streaming large result sets

Mon, 28 Jun 2010 22:20:12 GMT

Effectively an NHibernate-friendly cursor. I nice demonstration of consuming large amounts of data responsively without allocating the memory to store the entire result set.

robsosno commented on NHibernate: Streaming large result sets

Mon, 28 Jun 2010 20:07:37 GMT

Partial solution would be also to use Enumerable (if books table is not extra large): using (ISession s = OpenSession()) { var books = s.Enumerable("from Book") .List

gs commented on NHibernate: Streaming large result sets

Mon, 28 Jun 2010 19:40:00 GMT

__For reporting scenarios, there are better alternatives, usually (and before you ask, any reporting package will do. Right tool for the job, etc). I'll bite, what's everyone use? I've been using Quartz.Net to run heavy reporting jobs at night and as sort of a load balancer (so really I use NHibernate, as Quartz.net just triggers the report). I wasn't aware of any report specific tools. Of course searching ".NET Reporting" brings up a bunch of garbage ...

orip commented on NHibernate: Streaming large result sets

Sun, 27 Jun 2010 10:22:05 GMT

awesome - I guess you could also create a list that creates an IEnumerator that supplies the results one by one. Would the effect be similar? var books = new IterableList