improved performance on mssql4

gluon/dal.py

@@ -3458,15 +3458,21 @@ class MSSQL4Adapter(MSSQLAdapter):
     """ support for true pagination in MSSQL >= 2012"""
 
     def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
-        if not sql_o:
-            #if there is no orderby, we can't use the brand new statements
-            #that being said, developer chose its own poison, so be it random
-            sql_o += ' ORDER BY %s' % self.RANDOM()
         if limitby:
             (lmin, lmax) = limitby
-            sql_o += ' OFFSET %i ROWS FETCH NEXT %i ROWS ONLY' % (lmin, lmax - lmin)
+            if lmin == 0:
+                #top is still slightly faster, especially because
+                #web2py's default to fetch references is to not specify
+                #an orderby clause
+                sql_s += ' TOP %i' % lmax
+            else:
+                if not sql_o:
+                    #if there is no orderby, we can't use the brand new statements
+                    #that being said, developer chose its own poison, so be it random
+                    sql_o += ' ORDER BY %s' % self.RANDOM()
+                sql_o += ' OFFSET %i ROWS FETCH NEXT %i ROWS ONLY' % (lmin, lmax - lmin)
         return 'SELECT %s %s FROM %s%s%s;' % \
-            (sql_s, sql_f, sql_t, sql_w, sql_o)
+                (sql_s, sql_f, sql_t, sql_w, sql_o)
 
     def rowslice(self,rows,minimum=0,maximum=None):
         return rows