Use RAII to free select statement results

5 files changed, 73 insertions, 36 deletions

diff --git a/odb/mssql/object-result.txx b/odb/mssql/object-result.txx
index efaeae9..9f6b2d0 100644
--- a/odb/mssql/object-result.txx
+++ b/odb/mssql/object-result.txx
@@ -31,6 +31,9 @@ namespace odb
       }
 
       delete image_copy_;
+
+      if (!this->end_)
+        statement_->free_result ();
     }
 
     template <typename T>
@@ -129,7 +132,10 @@ namespace odb
       }
 
       if (statement_->fetch () == select_statement::no_data)
+      {
+        statement_->free_result ();
         this->end_ = true;
+      }
       else
       {
         cc.callback = &change_callback;
@@ -184,6 +190,9 @@ namespace odb
         cc.callback = 0;
       }
 
+      if (!this->end_)
+        statement_->free_result ();
+
       delete image_copy_;
     }
 
@@ -252,7 +261,10 @@ namespace odb
       }
 
       if (statement_->fetch () == select_statement::no_data)
+      {
+        statement_->free_result ();
         this->end_ = true;
+      }
       else
       {
         cc.callback = &change_callback;
diff --git a/odb/mssql/object-statements.txx b/odb/mssql/object-statements.txx
index c8753d2..01249d9 100644
--- a/odb/mssql/object-statements.txx
+++ b/odb/mssql/object-statements.txx
@@ -87,6 +87,10 @@ namespace odb
         if (!object_traits::find_ (*this, l.id))
           throw object_not_persistent ();
 
+        // Our find_() version delays result freeing.
+        //
+        auto_result ar (*find_);
+
         object_traits::callback (db, *l.obj, callback_event::pre_load);
 
         // Our calls to init/load below can result in additional delayed
@@ -95,7 +99,7 @@ namespace odb
         //
         object_traits::init (*l.obj, image (), &db);
         find_->stream_result ();
-        find_->free_result (); // Our find_() version delays result freeing.
+        ar.free ();
         object_traits::load_ (*this, *l.obj); // Load containers, etc.
 
         if (!delayed_.empty ())
diff --git a/odb/mssql/statement.cxx b/odb/mssql/statement.cxx
index 8c3870d..e6cd7b8 100644
--- a/odb/mssql/statement.cxx
+++ b/odb/mssql/statement.cxx
@@ -694,13 +694,17 @@ namespace odb
     //
     // select_statement
     //
+    select_statement::
+    ~select_statement ()
+    {
+    }
 
     select_statement::
     select_statement (connection& conn,
                       const string& t,
                       binding& param,
                       binding& result)
-        : statement (conn, t), result_ (result), executed_ (false)
+        : statement (conn, t), result_ (result)
     {
       bind_param (param.bind, param.count);
       first_long_ = bind_result (result.bind, result.count);
@@ -712,7 +716,7 @@ namespace odb
                       binding& param,
                       binding& result,
                       bool ct)
-        : statement (conn, t, ct), result_ (result), executed_ (false)
+        : statement (conn, t, ct), result_ (result)
     {
       bind_param (param.bind, param.count);
       first_long_ = bind_result (result.bind, result.count);
@@ -720,7 +724,7 @@ namespace odb
 
     select_statement::
     select_statement (connection& conn, const string& t, binding& result)
-        : statement (conn, t), result_ (result), executed_ (false)
+        : statement (conn, t), result_ (result)
     {
       first_long_ = bind_result (result.bind, result.count);
     }
@@ -730,38 +734,18 @@ namespace odb
                       const char* t,
                       binding& result,
                       bool ct)
-        : statement (conn, t, ct), result_ (result), executed_ (false)
+        : statement (conn, t, ct), result_ (result)
     {
       first_long_ = bind_result (result.bind, result.count);
     }
 
-    select_statement::
-    ~select_statement ()
-    {
-      if (executed_)
-      {
-        try
-        {
-          free_result ();
-        }
-        catch (...)
-        {
-        }
-      }
-    }
-
     void select_statement::
     execute ()
     {
-      if (executed_)
-        free_result ();
-
       SQLRETURN r (statement::execute ());
 
       if (!SQL_SUCCEEDED (r))
         translate_error (r, conn_, stmt_);
-
-      executed_ = true;
     }
 
     select_statement::result select_statement::
@@ -786,17 +770,16 @@ namespace odb
     void select_statement::
     free_result ()
     {
-      if (executed_)
-      {
-        // If we cannot close the cursor, there is no point in trying again.
-        //
-        executed_ = false;
-
-        SQLRETURN r (SQLCloseCursor (stmt_));
+      // Use SQLFreeStmt(SQL_CLOSE) instead of SQLCloseCursor() to avoid an
+      // error if a cursor is already closed. This can happens, for example,
+      // if we are trying to close the cursor after the transaction has been
+      // committed (e.g., when destroying the query result) which also closes
+      // the cursor.
+      //
+      SQLRETURN r (SQLFreeStmt (stmt_, SQL_CLOSE));
 
-        if (!SQL_SUCCEEDED (r))
-          translate_error (r, conn_, stmt_);
-      }
+      if (!SQL_SUCCEEDED (r))
+        translate_error (r, conn_, stmt_);
     }
 
     //
diff --git a/odb/mssql/statement.hxx b/odb/mssql/statement.hxx
index eb95a35..86178e6 100644
--- a/odb/mssql/statement.hxx
+++ b/odb/mssql/statement.hxx
@@ -147,7 +147,39 @@ namespace odb
     private:
       binding& result_;
       std::size_t first_long_; // First long data column.
-      bool executed_;
+    };
+
+    struct LIBODB_MSSQL_EXPORT auto_result
+    {
+      explicit auto_result (select_statement& s): s_ (&s) {}
+      ~auto_result () {free ();}
+
+      // Extended interface to support delayed freeing.
+      //
+      auto_result (): s_ (0) {}
+
+      void
+      set (select_statement& s) {s_ = &s;}
+
+      void
+      free ()
+      {
+        if (s_ != 0)
+        {
+          s_->free_result ();
+          s_ = 0;
+        }
+      }
+
+      void
+      release () {s_ = 0;}
+
+    private:
+      auto_result (const auto_result&);
+      auto_result& operator= (const auto_result&);
+
+    private:
+      select_statement* s_;
     };
 
     class LIBODB_MSSQL_EXPORT insert_statement: public statement
diff --git a/odb/mssql/view-result.txx b/odb/mssql/view-result.txx
index de64438..a9b28a3 100644
--- a/odb/mssql/view-result.txx
+++ b/odb/mssql/view-result.txx
@@ -24,6 +24,9 @@ namespace odb
         cc.context = 0;
       }
 
+      if (!this->end_)
+        statement_->free_result ();
+
       delete image_copy_;
     }
 
@@ -92,7 +95,10 @@ namespace odb
       }
 
       if (statement_->fetch () == select_statement::no_data)
+      {
+        statement_->free_result ();
         this->end_ = true;
+      }
       else
       {
         cc.callback = &change_callback;