Change behavior of count(:limit => x, :offset => y) to limit/offset before counting.

2 files changed, 54 insertions, 11 deletions

diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index caf07a7357..1e8ce4fda7 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -65,7 +65,7 @@ class CalculationsTest < ActiveRecord::TestCase
     c = Account.sum(:credit_limit, :group => :firm_id)
     [1,6,2].each { |firm_id| assert c.keys.include?(firm_id) }
   end
-  
+
   def test_should_group_by_multiple_fields
     c = Account.count(:all, :group => ['firm_id', :credit_limit])
     [ [nil, 50], [1, 50], [6, 50], [6, 55], [9, 53], [2, 60] ].each { |firm_and_limit| assert c.keys.include?(firm_and_limit) }
@@ -109,27 +109,42 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal [2, 6], c.keys.compact
   end
 
-  def test_limit_with_offset_is_kept
+  def test_limit_should_apply_before_count
+    accounts = Account.limit(3).where('firm_id IS NOT NULL')
+
+    assert_equal 3, accounts.count(:firm_id)
+    assert_equal 3, accounts.select(:firm_id).count
+  end
+
+  def test_count_should_shortcut_with_limit_zero
+    accounts = Account.limit(0)
+
+    assert_no_queries { assert_equal 0, accounts.count }
+  end
+
+  def test_limit_is_kept
     return if current_adapter?(:OracleAdapter)
 
-    queries = assert_sql { Account.limit(1).offset(1).count }
+    queries = assert_sql { Account.limit(1).count }
     assert_equal 1, queries.length
     assert_match(/LIMIT/, queries.first)
-    assert_match(/OFFSET/, queries.first)
   end
 
-  def test_offset_without_limit_removes_offset
+  def test_offset_is_kept
+    return if current_adapter?(:OracleAdapter)
+
     queries = assert_sql { Account.offset(1).count }
     assert_equal 1, queries.length
-    assert_no_match(/LIMIT/, queries.first)
-    assert_no_match(/OFFSET/, queries.first)
+    assert_match(/OFFSET/, queries.first)
   end
 
-  def test_limit_without_offset_removes_limit
-    queries = assert_sql { Account.limit(1).count }
+  def test_limit_with_offset_is_kept
+    return if current_adapter?(:OracleAdapter)
+
+    queries = assert_sql { Account.limit(1).offset(1).count }
     assert_equal 1, queries.length
-    assert_no_match(/LIMIT/, queries.first)
-    assert_no_match(/OFFSET/, queries.first)
+    assert_match(/LIMIT/, queries.first)
+    assert_match(/OFFSET/, queries.first)
   end
 
   def test_no_limit_no_offset
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 37bbb17e74..e9c006d623 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -666,6 +666,34 @@ class RelationTest < ActiveRecord::TestCase
     assert_no_queries { assert_equal 5, best_posts.size }
   end
 
+  def test_size_with_limit
+    posts = Post.limit(6)
+
+    assert_queries(1) { assert_equal 6, posts.size }
+    assert ! posts.loaded?
+
+    best_posts = posts.where(:comments_count => 0)
+    best_posts.to_a # force load
+    assert_no_queries { assert_equal 5, best_posts.size }
+  end
+
+  def test_size_with_zero_limit
+    posts = Post.limit(0)
+
+    assert_no_queries { assert_equal 0, posts.size }
+    assert ! posts.loaded?
+
+    posts.to_a # force load
+    assert_no_queries { assert_equal 0, posts.size }
+  end
+
+  def test_empty_with_zero_limit
+    posts = Post.limit(0)
+
+    assert_no_queries { assert_equal true, posts.empty? }
+    assert ! posts.loaded?
+  end
+
   def test_count_complex_chained_relations
     posts = Post.select('comments_count').where('id is not null').group("author_id").where("comments_count > 0")