Figure out how to organize views for associations

#15

The idea is to allow unnamed views. They should be quite useful for associations, something like

User = Meta.new
  has_many :items
end

produces following meta document:

{
 // ...
 name: User,
 has_many_items: @#<reference to View document>
 // ... 
}

and View document is as follows:

{
 // ...
 meta: @#<reference to View meta>,
 reference_slotname: 'user', 
 meta: 'Item'
 // ...
}

WDYT?

Of course, we will address some edge cases to prevent spoiling databases with similar views — but that is rather optimization approach, so should be figured out a bit later.

Reported by Yurii Rashkovskii · April 28th, 2008 @ 06:39 AM

Activity

Oleg Andreev
I think things get easier when you do name a view like "has_many_{items}" or "{container}_has_many_{items}".
If we'd like to put all the "has_many" assocs into the very same View, we would do a generic "has_many_view" view with a key [ doc.belongs_to, "comment"|"whatever" ], so that items can be using a suffix. And also, we have to provide some useful aliasing for belongs_to to use comments.article instead of comments.belongs_to

April 28th, 2008 @ 08:21 AM
Yurii Rashkovskii
Please note that "{container}_has_many_{items}" will need to include nsurls for both container and items as well. Is that fine?

April 28th, 2008 @ 08:19 AM
Oleg Andreev
There is no need in nslurl for container: it is identified by UUID in a key.
For The Very Generic Has Many View, yes, we have to put a meta name along with its nsurl. So i would like not to try to put everything in a single big list, but to have a common view for the different containers and a particular association. Like "has_many_comments" view for comments (attached to any kind of container).
It is not really a problem to have some views duplicated. It is hidden under the has_many macro, anyway. But when you'd like to optimize some of the views, you may rebuild only one has_many view without affecting others.
My suggestion is to have views being specific for an association meta, but generic across all the assoc's containers.

April 28th, 2008 @ 08:30 AM

Yurii Rashkovskii

Title changed from Consider allowing unnamed views to Figure out how to organize views for associations

The picture you're trying to describe is not clear for me.

Here is an attempt to summarize:

Lets say we have a view for all has_many associations:

(the code below is just a sketch):

# View for documents that have associations
docs_with_assocs = View.define("DocumentsWithAssociations") do |view|
  def view.map(uuid, doc)
        r = doc.meta.slotnames.grep(/^has_many_/).map do |assoc_slotname|
              # emit pair with reference_slotname, meta and doc
        end
        r.empty? ? nil : r
  end
end

# Views for associations
View.define("HasManyAssociations") do |view|
   def view.map(uuid, doc)
         doc.slotnames.map |slotname|
            docs_with_assocs.find(:key => [slotname, doc.meta])
            # emit pairs for those documents that has appropriate associations defined in docs_with_assocs
         end
   end
end

Something like that or not?

April 28th, 2008 @ 08:52 AM

Yurii Rashkovskii
One of my concerns is that having N views to execute on each index update for N associations defined within database might be PIA

April 28th, 2008 @ 08:58 AM
Yurii Rashkovskii
// #14 has_many association based on Views had some useful code snippet but was resolved as duplicate for this ticket

April 28th, 2008 @ 09:00 AM
Oleg Andreev
1) By default, yes, a document will go through all the views. This can be optimized by describing a filtering view (or a list of views) which emits a list of relevant views for a particular document. See "PERSISTANCE & UPDATES" section of meta/papers/views.txt.
We may describe a scope of the view in several places: in a store setup, in a meta (see below) or the view itself. Depends on real situations we'll meet soon.
2) View naming issue: we may add a nsurl to a view name.
Like:
```
Article = Meta.new ... has_many :comments, :nsurl => "blah-blah"
BlogPost = Meta.new ... has_many :comments

# generates => 

View.define("has_many:Comment:http://ns.url") do 
  ...
end

Comment = Meta.new do
  update_views do |comment| # special callback on save to get a list of views to be updated
    Views["has_many:Comment:http://ns.url"]
  end
end

# view can be added to update_views callback this way:
# Comment.update_views << View["some_name"]
```
April 28th, 2008 @ 09:20 AM
Yurii Rashkovskii
- State changed from new to resolved
Whatever. Lets see how all this crap will work.

April 28th, 2008 @ 09:38 AM

Please Sign in or create a free account to add a new ticket.

With your very own profile, you can contribute to projects, track your activity, watch tickets, receive and update tickets through your email and much more.