Refactored get_limit_offset_sql() to DatabaseOperations.limit_offset_sql(). Refs #5106

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5959 bcc190cf-cafb-0310-a4f2-bffc1f526a37

10 files changed, 30 insertions, 44 deletions

diff --git a/django/db/backends/__init__.py b/django/db/backends/__init__.py
index 3f012eadff..e6776a19b7 100644
--- a/django/db/backends/__init__.py
+++ b/django/db/backends/__init__.py
@@ -109,3 +109,13 @@ class BaseDatabaseOperations(object):
         column.
         """
         return cursor.lastrowid
+
+    def limit_offset_sql(self, limit, offset=None):
+        """
+        Returns a LIMIT/OFFSET SQL clause, given a limit and optional offset.
+        """
+        # 'LIMIT 40 OFFSET 20'
+        sql = "LIMIT %s" % limit
+        if offset and offset != 0:
+            sql += " OFFSET %s" % offset
+        return sql
diff --git a/django/db/backends/ado_mssql/base.py b/django/db/backends/ado_mssql/base.py
index 02795fd0c1..19dd7278d2 100644
--- a/django/db/backends/ado_mssql/base.py
+++ b/django/db/backends/ado_mssql/base.py
@@ -100,13 +100,6 @@ dictfetchone = util.dictfetchone
 dictfetchmany = util.dictfetchmany
 dictfetchall  = util.dictfetchall
 
-def get_limit_offset_sql(limit, offset=None):
-    # TODO: This is a guess. Make sure this is correct.
-    sql = "LIMIT %s" % limit
-    if offset and offset != 0:
-        sql += " OFFSET %s" % offset
-    return sql
-
 def get_random_function_sql():
     return "RAND()"
 
diff --git a/django/db/backends/dummy/base.py b/django/db/backends/dummy/base.py
index e6547fa765..334e5146b7 100644
--- a/django/db/backends/dummy/base.py
+++ b/django/db/backends/dummy/base.py
@@ -43,7 +43,6 @@ quote_name = complain
 dictfetchone = complain
 dictfetchmany = complain
 dictfetchall = complain
-get_limit_offset_sql = complain
 get_random_function_sql = complain
 get_pk_default_value = complain
 get_max_name_length = ignore
diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index a9ca8e046a..259034b4bb 100644
--- a/django/db/backends/mysql/base.py
+++ b/django/db/backends/mysql/base.py
@@ -77,6 +77,13 @@ class DatabaseOperations(BaseDatabaseOperations):
     def fulltext_search_sql(self, field_name):
         return 'MATCH (%s) AGAINST (%%s IN BOOLEAN MODE)' % field_name
 
+    def limit_offset_sql(self, limit, offset=None):
+        # 'LIMIT 20,40'
+        sql = "LIMIT "
+        if offset and offset != 0:
+            sql += "%s," % offset
+        return sql + str(limit)
+
 class DatabaseWrapper(BaseDatabaseWrapper):
     ops = DatabaseOperations()
 
@@ -155,12 +162,6 @@ dictfetchone = util.dictfetchone
 dictfetchmany = util.dictfetchmany
 dictfetchall  = util.dictfetchall
 
-def get_limit_offset_sql(limit, offset=None):
-    sql = "LIMIT "
-    if offset and offset != 0:
-        sql += "%s," % offset
-    return sql + str(limit)
-
 def get_random_function_sql():
     return "RAND()"
 
diff --git a/django/db/backends/mysql_old/base.py b/django/db/backends/mysql_old/base.py
index 8497cc5983..5de2cbfda8 100644
--- a/django/db/backends/mysql_old/base.py
+++ b/django/db/backends/mysql_old/base.py
@@ -87,6 +87,13 @@ class DatabaseOperations(BaseDatabaseOperations):
     def fulltext_search_sql(self, field_name):
         return 'MATCH (%s) AGAINST (%%s IN BOOLEAN MODE)' % field_name
 
+    def limit_offset_sql(self, limit, offset=None):
+        # 'LIMIT 20,40'
+        sql = "LIMIT "
+        if offset and offset != 0:
+            sql += "%s," % offset
+        return sql + str(limit)
+
 class DatabaseWrapper(BaseDatabaseWrapper):
     ops = DatabaseOperations()
 
@@ -174,12 +181,6 @@ dictfetchone = util.dictfetchone
 dictfetchmany = util.dictfetchmany
 dictfetchall  = util.dictfetchall
 
-def get_limit_offset_sql(limit, offset=None):
-    sql = "LIMIT "
-    if offset and offset != 0:
-        sql += "%s," % offset
-    return sql + str(limit)
-
 def get_random_function_sql():
     return "RAND()"
 
diff --git a/django/db/backends/oracle/base.py b/django/db/backends/oracle/base.py
index f35586cbbc..df153378f0 100644
--- a/django/db/backends/oracle/base.py
+++ b/django/db/backends/oracle/base.py
@@ -62,6 +62,11 @@ class DatabaseOperations(BaseDatabaseOperations):
         cursor.execute('SELECT %s_sq.currval FROM dual' % sq_name)
         return cursor.fetchone()[0]
 
+    def limit_offset_sql(self, limit, offset=None):
+        # Limits and offset are too complicated to be handled here.
+        # Instead, they are handled in django/db/backends/oracle/query.py.
+        return ""
+
 class DatabaseWrapper(BaseDatabaseWrapper):
     ops = DatabaseOperations()
 
@@ -178,11 +183,6 @@ def get_field_cast_sql(db_type):
     else:
         return "%s%s"
 
-def get_limit_offset_sql(limit, offset=None):
-    # Limits and offset are too complicated to be handled here.
-    # Instead, they are handled in django/db/backends/oracle/query.py.
-    return ""
-
 def get_random_function_sql():
     return "DBMS_RANDOM.RANDOM"
 
diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index 1642a51d7e..4926ddf8d1 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -131,12 +131,6 @@ def dictfetchall(cursor):
     "Returns all rows from a cursor as a dict"
     return cursor.dictfetchall()
 
-def get_limit_offset_sql(limit, offset=None):
-    sql = "LIMIT %s" % limit
-    if offset and offset != 0:
-        sql += " OFFSET %s" % offset
-    return sql
-
 def get_random_function_sql():
     return "RANDOM()"
 
diff --git a/django/db/backends/postgresql_psycopg2/base.py b/django/db/backends/postgresql_psycopg2/base.py
index 9ba5c8a170..f8d8765e92 100644
--- a/django/db/backends/postgresql_psycopg2/base.py
+++ b/django/db/backends/postgresql_psycopg2/base.py
@@ -85,12 +85,6 @@ dictfetchone = util.dictfetchone
 dictfetchmany = util.dictfetchmany
 dictfetchall = util.dictfetchall
 
-def get_limit_offset_sql(limit, offset=None):
-    sql = "LIMIT %s" % limit
-    if offset and offset != 0:
-        sql += " OFFSET %s" % offset
-    return sql
-
 def get_random_function_sql():
     return "RANDOM()"
 
diff --git a/django/db/backends/sqlite3/base.py b/django/db/backends/sqlite3/base.py
index b1d7dc8db1..75c753ef22 100644
--- a/django/db/backends/sqlite3/base.py
+++ b/django/db/backends/sqlite3/base.py
@@ -115,12 +115,6 @@ def _sqlite_extract(lookup_type, dt):
         return None
     return str(getattr(dt, lookup_type))
 
-def get_limit_offset_sql(limit, offset=None):
-    sql = "LIMIT %s" % limit
-    if offset and offset != 0:
-        sql += " OFFSET %s" % offset
-    return sql
-
 def get_random_function_sql():
     return "RANDOM()"
 
diff --git a/django/db/models/query.py b/django/db/models/query.py
index faf469f1bf..df3be74632 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -555,7 +555,7 @@ class _QuerySet(object):
 
         # LIMIT and OFFSET clauses
         if self._limit is not None:
-            sql.append("%s " % backend.get_limit_offset_sql(self._limit, self._offset))
+            sql.append("%s " % connection.ops.limit_offset_sql(self._limit, self._offset))
         else:
             assert self._offset is None, "'offset' is not allowed without 'limit'"