Ayende @ Rahien

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Porting MVC Music Store to Raven: StoreController

We will start with the Index() method:

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There are one this in this code that bothers me, and that is that this code is going to perform two DB queries. But that is beside the point, since we are going to modify the whole thing.

And here is my port:

image

As you can see, it is pretty much the same, and not really that interesting. Let us see what else we have:

image

Something that is important to note here is that we are doing a search on the name of a genre. The problem is that the genre name isn’t the primary key, worse, there isn’t even an index on the name column. Now, admittedly, the genre table contains ten rows, but it is the principal of the thing. (If you are smart, you only have to be read the riot act by the DBA about non index queries in production once).

Now, it would be trivial for us to implement this in Raven using the same approach, but I don’t see a reason to do this. The genre that we get in the Browse method is dependant on the data that we return from the Index method, so there is no reason no to pass the id of the genre directly. I modified the Index() action to pass the entire genre, not just the genre name, and to pass the id back to the Browse() action, not the name.

I gotten started implementing this, but I got stuck on the association of Albums from the genre.

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Document database doesn’t normally have associations, and they don’t have joins. So how can we do this?

By now, you should be pretty familiar with the answer, we need to define an index :-)

// AlbumsByGenre
from album in docs.Albums
where album.Genre != null
select new { Genre = album.Genre.Id }

And this index allows us to write this code:

image

And finally, we have the GenreMenu:

image

Which we can port very easily:

image

And that is all for the StoreController

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Posted By: Ayende Rahien

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Comments

Rob Ashton
05/25/2010 01:54 PM by
Rob Ashton

Note to the uninitiated, this is now out of date and it is now possible to do strongly typed queries

.Where(x=>x.Genre == genre);

:)

tobi
05/25/2010 04:07 PM by
tobi

I think the index system is very nice. Simple, maintainable and fast.

configurator
05/25/2010 09:47 PM by
configurator

A few questions. (I haven't looked at the actual example but I believe I understand what's going on)

First, isn't the parameter to Browse passed in the url? In that case I'd much rather see /browse/jazz than /browse/17, wouldn't you?

Second, what is the static type of session.Query <genre?

And last, can you define a string primary key in Raven?

Ayende Rahien
05/25/2010 09:50 PM by
Ayende Rahien

configurator,

a) the key I used was the one the original application used.

b) yes, jazz is easier than 17, but I followed the path of the app.

c) all keys in Raven are strings

Peter Willis
06/13/2010 10:32 AM by
Peter Willis

"There are one this in this code that bothers me, and that is that this code is going to perform two DB queries. But that is beside the point, since we are going to modify the whole thing."

"One thing that bothers me is that this code is going to perform two DB queries. This is beside the point however, since we are going to modify the whole approach."

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