From d123588184dfecc286e8e06e16dc0383f435c051 Mon Sep 17 00:00:00 2001
From: Malcolm Tredinnick <malcolm.tredinnick@gmail.com>
Date: Mon, 12 Feb 2007 00:16:17 +0000
Subject: [PATCH] #fixed #2256 -- Made count() interact with slicing on
 QuerySets. Patch from SmileyChris.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@4488 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/db/models/query.py         | 16 ++++++++++++++--
 tests/modeltests/lookup/models.py | 11 +++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/django/db/models/query.py b/django/db/models/query.py
index 7a81910715..8a784be7c8 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -197,9 +197,12 @@ class QuerySet(object):
         "Performs a SELECT COUNT() and returns the number of records as an integer."
         counter = self._clone()
         counter._order_by = ()
+        counter._select_related = False
+        
+        offset = counter._offset
+        limit = counter._limit
         counter._offset = None
         counter._limit = None
-        counter._select_related = False
         
         try:
             select, sql, params = counter._get_sql_clause()
@@ -213,7 +216,16 @@ class QuerySet(object):
             cursor.execute("SELECT COUNT(DISTINCT(%s))" % id_col + sql, params)
         else:
             cursor.execute("SELECT COUNT(*)" + sql, params)
-        return cursor.fetchone()[0]
+        count = cursor.fetchone()[0]
+
+        # Apply any offset and limit constraints manually, since using LIMIT or
+        # OFFSET in SQL doesn't change the output of COUNT.
+        if offset:
+            count = max(0, count - offset)
+        if limit:
+            count = min(limit, count)
+
+        return count
 
     def get(self, *args, **kwargs):
         "Performs the SELECT and returns a single object matching the given keyword arguments."
diff --git a/tests/modeltests/lookup/models.py b/tests/modeltests/lookup/models.py
index d344710bef..106c97d3b4 100644
--- a/tests/modeltests/lookup/models.py
+++ b/tests/modeltests/lookup/models.py
@@ -58,6 +58,17 @@ Article 4
 >>> Article.objects.filter(headline__startswith='Blah blah').count()
 0L
 
+# count() should respect sliced query sets.
+>>> articles = Article.objects.all()
+>>> articles.count()
+7L
+>>> articles[:4].count()
+4
+>>> articles[1:100].count()
+6L
+>>> articles[10:100].count()
+0
+
 # Date and date/time lookups can also be done with strings.
 >>> Article.objects.filter(pub_date__exact='2005-07-27 00:00:00').count()
 3L