Fixed #404 -- Fixed random ordering in MySQL by abstracting random fu…

…nction into db backend modules. Thanks, mattycakes@gmail.com

git-svn-id: http://code.djangoproject.com/svn/django/trunk@615 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/db/__init__.py

@@ -38,6 +38,7 @@
 get_date_extract_sql = dbmod.get_date_extract_sql
 get_date_trunc_sql = dbmod.get_date_trunc_sql
 get_limit_offset_sql = dbmod.get_limit_offset_sql
+get_random_function_sql = dbmod.get_random_function_sql
 get_table_list = dbmod.get_table_list
 get_relations = dbmod.get_relations
 OPERATOR_MAPPING = dbmod.OPERATOR_MAPPING

django/core/db/backends/mysql.py

@@ -77,6 +77,9 @@ def get_limit_offset_sql(limit, offset=None):
         sql += "%s," % offset
     return sql + str(limit)
 
+def get_random_function_sql():
+    return "RAND()"
+
 def get_table_list(cursor):
     "Returns a list of table names in the current database."
     cursor.execute("SHOW TABLES")

django/core/db/backends/postgresql.py

@@ -77,6 +77,9 @@ def get_limit_offset_sql(limit, offset=None):
         sql += " OFFSET %s" % offset
     return sql
 
+def get_random_function_sql():
+    return "RANDOM()"
+
 def get_table_list(cursor):
     "Returns a list of table names in the current database."
     cursor.execute("""

django/core/db/backends/sqlite3.py

@@ -103,6 +103,9 @@ def get_limit_offset_sql(limit, offset=None):
         sql += " OFFSET %s" % offset
     return sql
 
+def get_random_function_sql():
+    return "RANDOM()"
+
 def _sqlite_date_trunc(lookup_type, dt):
     try:
         dt = typecasts.typecast_timestamp(dt)

django/core/meta/__init__.py

@@ -62,7 +62,7 @@ def orderlist2sql(order_list, opts, prefix=''):
         if f.startswith('-'):
             output.append('%s%s DESC' % (prefix, orderfield2column(f[1:], opts)))
         elif f == '?':
-            output.append('RANDOM()')
+            output.append(db.get_random_function_sql())
         else:
             output.append('%s%s ASC' % (prefix, orderfield2column(f, opts)))
     return ', '.join(output)
@@ -1319,7 +1319,7 @@ def function_get_sql_clause(opts, **kwargs):
     order_by = []
     for f in handle_legacy_orderlist(kwargs.get('order_by', opts.ordering)):
         if f == '?': # Special case.
-            order_by.append('RANDOM()')
+            order_by.append(db.get_random_function_sql())
         else:
             # Use the database table as a column prefix if it wasn't given,
             # and if the requested column isn't a custom SELECT.