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@@ -27,8 +27,11 @@ module ActiveRecord
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           else
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             @reflection.klass.count(:conditions => @counter_sql, :include => @reflection.options[:include])
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           end
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-          
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-          @target = [] and loaded if count == 0
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+
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+          # If there's nothing in the database and @target has no new records
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+          # we are certain the current target is an empty array. This is a
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+          # documented side-effect of the method that may avoid an extra SELECT.
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+          @target ||= [] and loaded if count == 0
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           if @reflection.options[:limit]
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             count = [ @reflection.options[:limit], count ].min

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@@ -391,6 +391,18 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
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     assert_equal 3, company.clients_of_firm.size
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   end
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+  def test_collection_size_twice_for_regressions
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+    post = posts(:thinking)
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+    assert_equal 0, post.readers.size
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+    # This test needs a post that has no readers, we assert it to ensure it holds,
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+    # but need to reload the post because the very call to #size hides the bug.
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+    post.reload
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+    post.readers.build
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+    size1 = post.readers.size
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+    size2 = post.readers.size
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+    assert_equal size1, size2
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+  end
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+
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   def test_build_many
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     company = companies(:first_firm)
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     new_clients = assert_no_queries { company.clients_of_firm.build([{"name" => "Another Client"}, {"name" => "Another Client II"}]) }