Strokedb StrokeDB

Problem: update relevant Views on document save.

Step 1. Run all the views with no prefiltering.

• Store keeps a simple list (set) of registered views.
• When Store#save! is called, it accesses this document and iterates over the listed views and updates them one by one.
• When view is defined it registers itself in a views list with Store#register_view(view).

Step 2. Some prefiltering.

When there are several hundreds of views in the system, running all the views for update can be very slow. The most common case: view should be run for a single meta (or possibly, a little set of metas). We may optimize this by defining a list of necessary metas for a particular view:

View.new("has_many_comments", :only => [Comment, SmallComment]) { }

• Store#register_view(view, [Meta1, Meta2,...]) is called then
• Store contains a hash map: { :rest => [list of views without :only option], meta1 => [list of views to consume meta1], meta2 => [...] }
• If View defines an :only option, it doesn't go to the :rest list, but is added to all the lists indexed by meta.
• When a document with several metas should be indexed only :rest views are updated and all the views under the selected metas in the store's index.

Example

View.new("generic") { }
View.new("comments", :only => ["comment"]) { }
View.new("comments_and_articles", :only => ["comment", "article"]) { }
View.new("sponsored", :only => ["sponsored_articles"]) { }

a = (Article + SponsoredArticle).create!(:title => "This is a sponsored article")
c = Comment.create!(:article => a, :text => "Hello")

In this situation "a" will be added to "generic" view, "comments_and_articles" view and "sponsored" view.

Comment "c" will be added to "generic", "comments" and "comments_and_articles" views.

nsurl can be attached to a meta name: "comment:http://some.url/"

(default is the same nsurl viewdoc has)

Step 3. Immediate and lazy view updates.

• Store may be configured to update some of the views in different manners (immediately, asynchronously, on schedule etc).
• It is a good idea to separate view definition and it's update strategy.

Possible syntax:

immediate = ImmediateViewUpdater.new
immediate << "view_name", "view_name2"
# this reindexes already registered views & is used to correctly index the views, which are added later. 
store.attach_view_updater(immediate)  

# Config builder DSL for the code above:

Config.view_updaters["immediate"] = ["view1", "view2"]
Config.view_updaters["nightly"] = ["fulltext", "weird_stats"]

Updaters incapsulate different update strategies. All the views, which are not defined in a particular updater are handled by a default ImmediateUpdater.