From 4f1606fcf2d64457b2645ea1af6821076d067a22 Mon Sep 17 00:00:00 2001
From: niphlod <niphlod@gmail.com>
Date: Fri, 20 Mar 2015 23:16:30 +0100
Subject: [PATCH] fixes #679

---
 gluon/sqlhtml.py | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/gluon/sqlhtml.py b/gluon/sqlhtml.py
index f788b1f8..a4556023 100644
--- a/gluon/sqlhtml.py
+++ b/gluon/sqlhtml.py
@@ -1958,7 +1958,8 @@ class SQLFORM(FORM):
              noconfirm=False,
              cache_count=None,
              client_side_delete=False,
-             ignore_common_filters=None):
+             ignore_common_filters=None,
+             auto_pagination=True):
 
         formstyle = formstyle or current.response.formstyle
 
@@ -2052,6 +2053,28 @@ class SQLFORM(FORM):
                 nrows = 0
             return nrows
 
+        def fix_orderby(orderby):
+            if not auto_pagination:
+                return orderby
+            # enforce always an ORDER clause to avoid
+            # pagination errors. field_id is needed anyhow,
+            # is unique and usually indexed. See issue #679
+            if not orderby:
+                orderby = field_id
+            else:
+                if isinstance(orderby, Expression):
+                    if orderby.first:
+                        # here we're with a DESC order on a field
+                        # stored as orderby.first
+                        if orderby.first is not field_id:
+                            orderby = orderby | field_id
+                    else:
+                        # here we're with an ASC order on a field
+                        # stored as orderby
+                        if orderby is not field_id:
+                            orderby = orderby | field_id
+            return orderby
+
         def url(**b):
             b['args'] = args + b.get('args', [])
             localvars = request.get_vars.copy()
@@ -2313,6 +2336,8 @@ class SQLFORM(FORM):
                     else:
                         orderby = (order[:1] == '~' and ~sort_field) or sort_field
 
+            orderby = fix_orderby(orderby)
+
             expcolumns = [str(f) for f in columns]
             selectable_columns = [str(f) for f in columns if not isinstance(f, Field.Virtual)]
             if export_type.endswith('with_hidden_cols'):
@@ -2524,6 +2549,9 @@ class SQLFORM(FORM):
             limitby = (paginate * page, paginate * (page + 1))
         else:
             limitby = None
+
+        orderby = fix_orderby(orderby)
+
         try:
             table_fields = [field for field in fields
                             if (field.tablename in tablenames and