emmanuel · October 18, 2011 23:50 · Oct 18, 2011 · Oct 17, 2011 · Sep 30, 2011 · Sep 27, 2011
diff --git a/dm_el.rb b/dm_el.rb
@@ -7,7 +7,7 @@
 require 'dm-core'
 require 'dm-constraints'
 require 'dm-migrations'
-require 'eager_loading'
+require File.expand_path('../eager_loading', __FILE__)
 
 DataMapper::Logger.new($stdout, :debug)
 DataMapper.setup(:default, "sqlite3://#{Dir.pwd}/db.sqlite")

diff --git a/eager_loading.rb b/eager_loading.rb
@@ -1,34 +1,9 @@
 # manual eager loading for DataMapper
-# adapted from Chris Corbyn: https://gist.github.com/1244491#gistcomment-56797
 module EagerLoading
 
   def eager_load(query_path)
-    scope = self
-
-    query_path.relationships.each do |relation|
-      source_key = relation.source_key.first # TODO: rename
-      target_key = relation.target_key.first # TODO: rename
-
-      # for each level in the query path, collect all the resources referencing
-      # keys at the current scope
-      next_scope = relation.target_model.all(target_key.name => scope.
-          collect(&:"#{source_key.name}"))
-
-      # map target keys to the resources that exist for them
-      links = next_scope.inject({}) do |map, resource|
-        map.merge(target_key.get(resource) => [resource]) { |k, v1, v2| v1 + v2 }
-      end
-
-      # now pre-load those from the map
-      scope.each do |parent|
-        if links.key?(source_key.get(parent))
-          parent.instance_variable_set(:"@#{relation.name}",
-              links[source_key.get(parent)])
-        end
-      end
-
-      # and step into the next nesting level
-      scope = next_scope
+    query_path.relationships.inject(self) do |collection, relationship|
+      relationship.eager_load(collection)
     end
 
     self

diff --git a/dm_el.rb b/dm_el.rb
@@ -7,6 +7,7 @@
 require 'dm-core'
 require 'dm-constraints'
 require 'dm-migrations'
+require 'eager_loading'
 
 DataMapper::Logger.new($stdout, :debug)
 DataMapper.setup(:default, "sqlite3://#{Dir.pwd}/db.sqlite")
@@ -89,7 +90,7 @@ class Manufacturer
   end
 end
 
-puts "", '[INFO] test case C    ===== /!\ n+1 hazard ===='
+puts "", "[INFO] test case C    ===== /!\ n+1 hazard ===="
 people = Person.all
 people.each do |person|
   person.vehicles.each do |vehicle|
@@ -98,3 +99,13 @@ class Manufacturer
     end
   end
 end
+
+puts "", "[INFO] test case D"
+people = Person.all
+people.eager_load(Person.vehicles.components).each do |person|
+  person.vehicles.each do |vehicle|
+    vehicle.components.each do |component|
+      puts sprintf("%-10s %-10s %-10s", person.name, vehicle.name, component.name)
+    end
+  end
+end
diff --git a/eager_loading.rb b/eager_loading.rb
@@ -0,0 +1,39 @@
+# manual eager loading for DataMapper
+# adapted from Chris Corbyn: https://gist.github.com/1244491#gistcomment-56797
+module EagerLoading
+
+  def eager_load(query_path)
+    scope = self
+
+    query_path.relationships.each do |relation|
+      source_key = relation.source_key.first # TODO: rename
+      target_key = relation.target_key.first # TODO: rename
+
+      # for each level in the query path, collect all the resources referencing
+      # keys at the current scope
+      next_scope = relation.target_model.all(target_key.name => scope.
+          collect(&:"#{source_key.name}"))
+
+      # map target keys to the resources that exist for them
+      links = next_scope.inject({}) do |map, resource|
+        map.merge(target_key.get(resource) => [resource]) { |k, v1, v2| v1 + v2 }
+      end
+
+      # now pre-load those from the map
+      scope.each do |parent|
+        if links.key?(source_key.get(parent))
+          parent.instance_variable_set(:"@#{relation.name}",
+              links[source_key.get(parent)])
+        end
+      end
+
+      # and step into the next nesting level
+      scope = next_scope
+    end
+
+    self
+  end
+
+end
+
+DataMapper::Collection.send(:include, EagerLoading)
diff --git a/dm_el.rb b/dm_el.rb
@@ -89,7 +89,7 @@ class Manufacturer
   end
 end
 
-puts "", "[INFO] test case C"
+puts "", '[INFO] test case C    ===== /!\ n+1 hazard ===='
 people = Person.all
 people.each do |person|
   person.vehicles.each do |vehicle|

diff --git a/dm_el.rb b/dm_el.rb
@@ -85,7 +85,7 @@ class Manufacturer
 people = Person.all
 people.each do |person|
   person.vehicles.each do |vehicle|
-    puts sprintf("%-20s %-20s", person.name, vehicle.name)
+    puts sprintf("%-10s %-10s", person.name, vehicle.name)
   end
 end
 
@@ -94,7 +94,7 @@ class Manufacturer
 people.each do |person|
   person.vehicles.each do |vehicle|
     vehicle.components.each do |component|
-      puts sprintf("%-20s %-20s %-20s", person.name, vehicle.name, component.name)
+      puts sprintf("%-10s %-10s %-10s", person.name, vehicle.name, component.name)
     end
   end
 end
diff --git a/run.sh b/run.sh
@@ -3,4 +3,4 @@
 rm db.sqlite
 
 # reformat SQL queries for readability
-./dm_el.rb | perl -pe 's|SELECT .*? (FROM ".*?" )(.*)|\1SELECT ... \2|'
+bundle exec ./dm_el.rb | perl -pe 's#SELECT .*? (FROM ".*?" )(.*)#\1SELECT ... \2#'
diff --git a/dm_el.rb b/dm_el.rb
@@ -77,6 +77,19 @@ class Manufacturer
 
 # retrieve data
 
+puts "", "[INFO] test case A"
+person = Person.get!(1)
+puts person.vehicles.components.manufacturer.map(&:name).join(", ")
+
+puts "", "[INFO] test case B"
+people = Person.all
+people.each do |person|
+  person.vehicles.each do |vehicle|
+    puts sprintf("%-20s %-20s", person.name, vehicle.name)
+  end
+end
+
+puts "", "[INFO] test case C"
 people = Person.all
 people.each do |person|
   person.vehicles.each do |vehicle|

diff --git a/run.sh b/run.sh
@@ -0,0 +1,6 @@
+#!/usr/bin/env sh
+
+rm db.sqlite
+
+# reformat SQL queries for readability
+./dm_el.rb | perl -pe 's|SELECT .*? (FROM ".*?" )(.*)|\1SELECT ... \2|'
diff --git a/dm_el.rb b/dm_el.rb
@@ -74,3 +74,14 @@ class Manufacturer
         :manufacturer => Manufacturer.create(:name => "VW"))
   ])
 ])
+
+# retrieve data
+
+people = Person.all
+people.each do |person|
+  person.vehicles.each do |vehicle|
+    vehicle.components.each do |component|
+      puts sprintf("%-20s %-20s %-20s", person.name, vehicle.name, component.name)
+    end
+  end
+end
diff --git a/dm_el.rb b/dm_el.rb
@@ -17,11 +17,11 @@ class Person
   property :id, Serial
   property :name, String, :required => true
 
-  has n, :cars
+  has n, :vehicles
 
 end
 
-class Car
+class Vehicle
   include DataMapper::Resource
 
   property :id, Serial
@@ -50,3 +50,27 @@ class Manufacturer
 end
 
 DataMapper.auto_migrate!
+
+# generate test data
+
+Person.create(:name => "FND", :vehicles => [
+  Vehicle.create(:name => "Taurus", :components => [
+    Component.create(:name => "engine",
+        :manufacturer => Manufacturer.create(:name => "Ford")),
+    Component.create(:name => "radio",
+        :manufacturer => Manufacturer.create(:name => "Bose"))
+  ]),
+  Vehicle.create(:name => "fixie", :components => [
+    Component.create(:name => "frame",
+        :manufacturer => Manufacturer.create(:name => "Campagnolo")),
+    Component.create(:name => "breaks",
+        :manufacturer => Manufacturer.create(:name => "Shimano"))
+  ])
+])
+
+Person.create(:name => "tillsc", :vehicles => [
+  Vehicle.create(:name => "Golf", :components => [
+    Component.create(:name => "engine",
+        :manufacturer => Manufacturer.create(:name => "VW"))
+  ])
+])
diff --git a/dm_el.rb b/dm_el.rb
@@ -9,7 +9,7 @@
 require 'dm-migrations'
 
 DataMapper::Logger.new($stdout, :debug)
-DataMapper.setup(:default, "sqlite3://db.sqlite")
+DataMapper.setup(:default, "sqlite3://#{Dir.pwd}/db.sqlite")
 
 class Person
   include DataMapper::Resource

diff --git a/.gitignore b/.gitignore
@@ -0,0 +1 @@
+Gemfile.lock
diff --git a/Gemfile b/Gemfile
@@ -0,0 +1,8 @@
+source :rubygems
+
+DM_VERSION    = '~> 1.2.0.rc2'
+
+gem 'dm-core', DM_VERSION
+gem 'dm-constraints', DM_VERSION
+gem 'dm-migrations', DM_VERSION
+gem 'dm-sqlite-adapter', DM_VERSION
diff --git a/dm_el.rb b/dm_el.rb
diff --git a/dm_el.rb b/dm_el.rb
@@ -0,0 +1,52 @@
+#!/usr/bin/env ruby
+# encoding: UTF-8
+
+# test case for eager loading of nested associations with DataMapper
+
+require 'rubygems'
+require 'dm-core'
+require 'dm-constraints'
+require 'dm-migrations'
+
+DataMapper::Logger.new($stdout, :debug)
+DataMapper.setup(:default, "sqlite3://db.sqlite")
+
+class Person
+  include DataMapper::Resource
+
+  property :id, Serial
+  property :name, String, :required => true
+
+  has n, :cars
+
+end
+
+class Car
+  include DataMapper::Resource
+
+  property :id, Serial
+  property :name, String, :required => true
+
+  has n, :components
+
+end
+
+class Component
+  include DataMapper::Resource
+
+  property :id, Serial
+  property :name, String, :required => true
+
+  belongs_to :manufacturer
+
+end
+
+class Manufacturer
+  include DataMapper::Resource
+
+  property :id, Serial
+  property :name, String, :required => true
+
+end
+
+DataMapper.auto_migrate!
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