From cabb43409d61fbaec01ac3a8960dd7d599290416 Mon Sep 17 00:00:00 2001
From: Steffen Bartsch <sbartsch@tzi.org>
Date: Tue, 24 Feb 2009 22:51:01 +0100
Subject: [PATCH] Added :join_operator parameter to find, letting you choose the join operator for hash joins

---
 activerecord/lib/active_record/base.rb |   15 +++++++++++----
 activerecord/test/cases/finder_test.rb |   14 ++++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 55ab1fa..7de3c9e 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -549,6 +549,8 @@ module ActiveRecord #:nodoc:
       #   or an array containing a mixture of both strings and named associations.
       #   If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table's columns.
       #   Pass <tt>:readonly => false</tt> to override.
+      # * <tt>:join_operator</tt> - If using <tt>:joins</tt> in hash form, you can pass <tt>:left_join</tt> in here to cause <tt>LEFT JOINs</tt> to be used
+      #   for joining associations.  This defaults to <tt>:inner_join</tt>.
       # * <tt>:include</tt> - Names associations that should be loaded alongside. The symbols named refer
       #   to already defined associations. See eager loading under Associations.
       # * <tt>:select</tt> - By default, this is "*" as in "SELECT * FROM", but can be changed if you, for example, want to do a join but not
@@ -1692,7 +1694,7 @@ module ActiveRecord #:nodoc:
           sql  = "SELECT #{options[:select] || (scope && scope[:select]) || default_select(options[:joins] || (scope && scope[:joins]))} "
           sql << "FROM #{(scope && scope[:from]) || options[:from] || quoted_table_name} "
 
-          add_joins!(sql, options[:joins], scope)
+          add_joins!(sql, options[:joins], scope, options[:join_operator])
           add_conditions!(sql, options[:conditions], scope)
 
           add_group!(sql, options[:group], options[:having], scope)
@@ -1785,7 +1787,7 @@ module ActiveRecord #:nodoc:
         end
 
         # The optional scope argument is for the current <tt>:find</tt> scope.
-        def add_joins!(sql, joins, scope = :auto)
+        def add_joins!(sql, joins, scope = :auto, join_operator = :inner_join)
           scope = scope(:find) if :auto == scope
           merged_joins = scope && scope[:joins] && joins ? merge_joins(scope[:joins], joins) : (joins || scope && scope[:joins])
           case merged_joins
@@ -1793,7 +1795,12 @@ module ActiveRecord #:nodoc:
             if array_of_strings?(merged_joins)
               sql << merged_joins.join(' ') + " "
             else
-              join_dependency = ActiveRecord::Associations::ClassMethods::InnerJoinDependency.new(self, merged_joins, nil)
+              join_dependency =
+                if join_operator == :left_join
+                  ActiveRecord::Associations::ClassMethods::JoinDependency.new(self, merged_joins, nil)
+                else
+                  ActiveRecord::Associations::ClassMethods::InnerJoinDependency.new(self, merged_joins, nil)
+                end
               sql << " #{join_dependency.join_associations.collect { |assoc| assoc.association_join }.join} "
             end
           when String
@@ -2400,7 +2407,7 @@ module ActiveRecord #:nodoc:
           end
         end
 
-        VALID_FIND_OPTIONS = [ :conditions, :include, :joins, :limit, :offset,
+        VALID_FIND_OPTIONS = [ :conditions, :include, :joins, :join_operator, :limit, :offset,
                                :order, :select, :readonly, :group, :having, :from, :lock ]
 
         def validate_find_options(options) #:nodoc:
diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index ee8f490..a549cae 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -994,6 +994,20 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal 1, person_with_reader_and_post.size
   end
 
+  def test_joins_with_left_join_operator
+    posts_with_or_without_categorizations_string_join = Post.find(
+      :all,
+      :joins => "LEFT JOIN categorizations ON categorizations.post_id = posts.id"
+    )
+    posts_with_or_without_categorizations_hash_join = Post.find(
+      :all,
+      :joins => :categorizations,
+      :join_operator => :left_join
+    )
+    assert_equal posts_with_or_without_categorizations_string_join.size,
+      posts_with_or_without_categorizations_hash_join.size
+  end
+
   def test_find_by_id_with_conditions_with_or
     assert_nothing_raised do
       Post.find([1,2,3],
-- 
1.5.4.3