initial implementation of cross-engine join

Conflicts:

	lib/arel/engines/memory/relations/array.rb
	lib/arel/engines/sql/primitives.rb

1 files changed, 31 insertions, 0 deletions

diff --git a/spec/arel/engines/memory/integration/joins/cross_engine_spec.rb b/spec/arel/engines/memory/integration/joins/cross_engine_spec.rb
new file mode 100644
index 0000000000..dd923ee6eb
--- /dev/null
+++ b/spec/arel/engines/memory/integration/joins/cross_engine_spec.rb
@@ -0,0 +1,31 @@
+require File.join(File.dirname(__FILE__), '..', '..', '..', '..', '..', 'spec_helper')
+
+module Arel
+  describe Join do
+    before do
+      @users = Array.new([
+        [1, 'bryan' ],
+        [2, 'emilio' ],
+        [3, 'nick']
+      ], [:id, :name])
+      @photos = Table.new(:photos)
+      @photos.delete
+      @photos                                                                              \
+        .insert(@photos[:id] => 1, @photos[:user_id] => 1, @photos[:camera_id] => 6) \
+        .insert(@photos[:id] => 2, @photos[:user_id] => 2, @photos[:camera_id] => 42)
+    end
+    
+    it 'joins across engines' do
+      @users                                         \
+        .join(@photos)                               \
+          .on(@users[:id].eq(@photos[:user_id]))     \
+        .project(@users[:name], @photos[:camera_id]) \
+      .let do |relation|
+        relation.call.should == [
+          Row.new(relation, ['bryan', '6']),
+          Row.new(relation, ['emilio', '42'])
+        ]
+      end
+    end
+  end
+end
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