Fixed #8408 -- Added ModelAdmin.show_full_result_count to avoid COUNT() query.

Thanks lidaobing for the suggestion.

8 files changed, 50 insertions, 7 deletions

diff --git a/django/contrib/admin/options.py b/django/contrib/admin/options.py
index f7fce09ddc..6edae7a5c5 100644
--- a/django/contrib/admin/options.py
+++ b/django/contrib/admin/options.py
@@ -110,6 +110,7 @@ class BaseModelAdmin(six.with_metaclass(forms.MediaDefiningClass)):
     readonly_fields = ()
     ordering = None
     view_on_site = True
+    show_full_result_count = True
 
     # Validation of ModelAdmin definitions
     # Old, deprecated style:
diff --git a/django/contrib/admin/templates/admin/change_list.html b/django/contrib/admin/templates/admin/change_list.html
index ca0080e3be..e99b1e0a6e 100644
--- a/django/contrib/admin/templates/admin/change_list.html
+++ b/django/contrib/admin/templates/admin/change_list.html
@@ -87,9 +87,9 @@
       {% endif %}
 
       {% block result_list %}
-          {% if action_form and actions_on_top and cl.full_result_count %}{% admin_actions %}{% endif %}
+          {% if action_form and actions_on_top and cl.show_admin_actions %}{% admin_actions %}{% endif %}
           {% result_list cl %}
-          {% if action_form and actions_on_bottom and cl.full_result_count %}{% admin_actions %}{% endif %}
+          {% if action_form and actions_on_bottom and cl.show_admin_actions %}{% admin_actions %}{% endif %}
       {% endblock %}
       {% block pagination %}{% pagination cl %}{% endblock %}
       </form>
diff --git a/django/contrib/admin/templates/admin/search_form.html b/django/contrib/admin/templates/admin/search_form.html
index c9b626d18f..4cc24604f7 100644
--- a/django/contrib/admin/templates/admin/search_form.html
+++ b/django/contrib/admin/templates/admin/search_form.html
@@ -6,7 +6,7 @@
 <input type="text" size="40" name="{{ search_var }}" value="{{ cl.query }}" id="searchbar" />
 <input type="submit" value="{% trans 'Search' %}" />
 {% if show_result_count %}
-    <span class="small quiet">{% blocktrans count counter=cl.result_count %}{{ counter }} result{% plural %}{{ counter }} results{% endblocktrans %} (<a href="?{% if cl.is_popup %}_popup=1{% endif %}">{% blocktrans with full_result_count=cl.full_result_count %}{{ full_result_count }} total{% endblocktrans %}</a>)</span>
+    <span class="small quiet">{% blocktrans count counter=cl.result_count %}{{ counter }} result{% plural %}{{ counter }} results{% endblocktrans %} (<a href="?{% if cl.is_popup %}_popup=1{% endif %}">{% if cl.show_full_result_count %}{% blocktrans with full_result_count=cl.full_result_count %}{{ full_result_count }} total{% endblocktrans %}{% else %}{% trans "Show all" %}{% endif %}</a>)</span>
 {% endif %}
 {% for pair in cl.params.items %}
     {% ifnotequal pair.0 search_var %}<input type="hidden" name="{{ pair.0 }}" value="{{ pair.1 }}"/>{% endifnotequal %}
diff --git a/django/contrib/admin/views/main.py b/django/contrib/admin/views/main.py
index 1f42310f8e..1fcc774657 100644
--- a/django/contrib/admin/views/main.py
+++ b/django/contrib/admin/views/main.py
@@ -177,10 +177,13 @@ class ChangeList(object):
         # Perform a slight optimization:
         # full_result_count is equal to paginator.count if no filters
         # were applied
-        if self.get_filters_params() or self.params.get(SEARCH_VAR):
-            full_result_count = self.root_queryset.count()
+        if self.model_admin.show_full_result_count:
+            if self.get_filters_params() or self.params.get(SEARCH_VAR):
+                full_result_count = self.root_queryset.count()
+            else:
+                full_result_count = result_count
         else:
-            full_result_count = result_count
+            full_result_count = None
         can_show_all = result_count <= self.list_max_show_all
         multi_page = result_count > self.list_per_page
 
@@ -194,6 +197,10 @@ class ChangeList(object):
                 raise IncorrectLookupParameters
 
         self.result_count = result_count
+        self.show_full_result_count = self.model_admin.show_full_result_count
+        # Admin actions are shown if there is at least one entry
+        # or if entries are not counted because show_full_result_count is disabled
+        self.show_admin_actions = self.show_full_result_count or bool(full_result_count)
         self.full_result_count = full_result_count
         self.result_list = result_list
         self.can_show_all = can_show_all
diff --git a/docs/ref/contrib/admin/index.txt b/docs/ref/contrib/admin/index.txt
index ca55df3ce7..bf34fa47f1 100644
--- a/docs/ref/contrib/admin/index.txt
+++ b/docs/ref/contrib/admin/index.txt
@@ -1160,6 +1160,19 @@ subclass::
     :meth:`ModelAdmin.get_search_results` to provide additional or alternate
     search behavior.
 
+.. attribute:: ModelAdmin.show_full_result_count
+
+    .. versionadded:: 1.8
+
+    Set ``show_full_result_count`` to control whether the full count of objects
+    should be displayed on a filtered admin page (e.g. ``99 results (103 total)``).
+    If this option is set to ``False``, a text like ``99 results (Show all)``
+    is displayed instead.
+
+    The default of ``show_full_result_count=True`` generates a query to perform
+    a full count on the table which can be expensive if the table contains a
+    large number of rows.
+
 .. attribute:: ModelAdmin.view_on_site
 
     .. versionadded:: 1.7
diff --git a/docs/releases/1.8.txt b/docs/releases/1.8.txt
index 5c28840c50..c77b40a6a3 100644
--- a/docs/releases/1.8.txt
+++ b/docs/releases/1.8.txt
@@ -72,6 +72,10 @@ Minor features
   <django.contrib.admin.AdminSite.site_url>` in order to display a link to the
   front-end site.
 
+* You can now specify :attr:`ModelAdmin.show_full_result_count
+  <django.contrib.admin.ModelAdmin.show_full_result_count>` to control whether
+  or not the full count of objects should be displayed on a filtered admin page.
+
 :mod:`django.contrib.auth`
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/tests/admin_views/admin.py b/tests/admin_views/admin.py
index 077d64b50d..7caca29c7b 100644
--- a/tests/admin_views/admin.py
+++ b/tests/admin_views/admin.py
@@ -327,6 +327,7 @@ class LanguageAdmin(admin.ModelAdmin):
 
 
 class RecommendationAdmin(admin.ModelAdmin):
+    show_full_result_count = False
     search_fields = ('=titletranslation__text', '=recommender__titletranslation__text',)
 
 
diff --git a/tests/admin_views/tests.py b/tests/admin_views/tests.py
index c9b946ac5e..88539d4684 100644
--- a/tests/admin_views/tests.py
+++ b/tests/admin_views/tests.py
@@ -2474,11 +2474,28 @@ class AdminSearchTest(TestCase):
         """
         Test presence of reset link in search bar ("1 result (_x total_)").
         """
-        response = self.client.get('/test_admin/admin/admin_views/person/?q=Gui')
+        #   1 query for session + 1 for fetching user
+        # + 1 for filtered result + 1 for filtered count
+        # + 1 for total count
+        with self.assertNumQueries(5):
+            response = self.client.get('/test_admin/admin/admin_views/person/?q=Gui')
         self.assertContains(response,
             """<span class="small quiet">1 result (<a href="?">3 total</a>)</span>""",
             html=True)
 
+    def test_no_total_count(self):
+        """
+        #8408 -- "Show all" should be displayed instead of the total count if
+        ModelAdmin.show_full_result_count is False.
+        """
+        #   1 query for session + 1 for fetching user
+        # + 1 for filtered result + 1 for filtered count
+        with self.assertNumQueries(4):
+            response = self.client.get('/test_admin/admin/admin_views/recommendation/?q=bar')
+        self.assertContains(response,
+            """<span class="small quiet">1 result (<a href="?">Show all</a>)</span>""",
+            html=True)
+
 
 @override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',),
     ROOT_URLCONF="admin_views.urls")