From f6eda10b4014ea75af1be88ab3498618e390ea47 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 16 Sep 2013 08:20:00 +0200
Subject: Diagnose (potentially) empty UPDATE statements with ROWVERSION

---
 odb/common.cxx                  | 26 ++++++++++++++++++++++++--
 odb/common.hxx                  |  8 ++++++++
 odb/relational/mssql/source.cxx | 33 +++++++++++++++++++++++++++++++--
 3 files changed, 63 insertions(+), 4 deletions(-)

diff --git a/odb/common.cxx b/odb/common.cxx
index 365fe19..f52cee6 100644
--- a/odb/common.cxx
+++ b/odb/common.cxx
@@ -270,12 +270,24 @@ traverse_view (semantics::class_& c)
 }
 
 void object_columns_base::
+traverse_pre (semantics::nameable&)
+{
+}
+
+void object_columns_base::
+traverse_post (semantics::nameable&)
+{
+}
+
+void object_columns_base::
 traverse (semantics::data_member& m,
           semantics::type& t,
           std::string const& kp,
           std::string const& dn,
           semantics::class_* to)
 {
+  traverse_pre (m);
+
   semantics::class_* oto (context::top_object);
 
   if (to != 0)
@@ -305,6 +317,8 @@ traverse (semantics::data_member& m,
 
   root_ = 0;
   context::top_object = oto;
+
+  traverse_post (m);
 }
 
 void object_columns_base::
@@ -320,7 +334,10 @@ traverse (semantics::class_& c)
   bool f (top_level_);
 
   if (top_level_)
+  {
+    traverse_pre (c);
     top_level_ = false;
+  }
   else
   {
     // Unless requested otherwise, don't go into bases if we are a derived
@@ -365,8 +382,13 @@ traverse (semantics::class_& c)
       context::top_object = 0;
   }
 
-  if (f && !first_)
-    flush ();
+  if (f)
+  {
+    if (!first_)
+      flush ();
+
+    traverse_post (c);
+  }
 }
 
 void object_columns_base::
diff --git a/odb/common.hxx b/odb/common.hxx
index c4ecbaf..0fcd481 100644
--- a/odb/common.hxx
+++ b/odb/common.hxx
@@ -219,6 +219,14 @@ struct object_columns_base: traversal::class_, virtual context
   virtual bool
   section_test (data_member_path const&);
 
+  // Start/end traversal callbacks.
+  //
+  virtual void
+  traverse_pre (semantics::nameable&);
+
+  virtual void
+  traverse_post (semantics::nameable&);
+
 public:
   object_columns_base (bool first = true,
                        column_prefix const& cp = column_prefix (),
diff --git a/odb/relational/mssql/source.cxx b/odb/relational/mssql/source.cxx
index 8274b50..83096ab 100644
--- a/odb/relational/mssql/source.cxx
+++ b/odb/relational/mssql/source.cxx
@@ -35,7 +35,8 @@ namespace relational
       //
       struct object_columns: relational::object_columns, context
       {
-        object_columns (base const& x): base (x) {}
+        object_columns (base const& x)
+          : base (x), rowversion_ (false), column_count_ (0) {}
 
         virtual bool
         column (semantics::data_member& m,
@@ -55,11 +56,39 @@ namespace relational
           {
             sql_type t (parse_sql_type (column_type (), m));
             if (t.type == sql_type::ROWVERSION)
+            {
+              rowversion_ = true;
               return false;
+            }
           }
 
-          return base::column (m, table, column);
+          bool r (base::column (m, table, column));
+
+          // Count the number of columns in the UPDATE statement, but
+          // excluding soft-deleted.
+          //
+          if (sk_ == statement_update && r && !deleted (member_path_))
+            column_count_++;
+
+          return r;
+        }
+
+        virtual void
+        traverse_post (semantics::nameable& n)
+        {
+          if (rowversion_ && column_count_ == 0)
+          {
+            location l (n.location ());
+            error (l) << "ROWVERSION in an object without any readwrite "
+              "data members" << endl;
+            error (l) << "UPDATE statement will be empty" << endl;
+            throw operation_failed ();
+          }
         }
+
+      private:
+        bool rowversion_;
+        size_t column_count_;
       };
       entry<object_columns> object_columns_;
 
-- 
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