From 9542fdc4434c3af3eaed91bf10e5b487044d8cc7 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 7 Mar 2012 10:21:07 +0200
Subject: Use RAII to free select statement results

---
 odb/mysql/object-result.txx | 16 ++++++++++++++++
 odb/mysql/statement.cxx     | 39 +++++++++++++++++++--------------------
 odb/mysql/statement.hxx     | 14 ++++++++++++++
 odb/mysql/view-result.txx   |  8 ++++++++
 4 files changed, 57 insertions(+), 20 deletions(-)

diff --git a/odb/mysql/object-result.txx b/odb/mysql/object-result.txx
index 81770c3..8144578 100644
--- a/odb/mysql/object-result.txx
+++ b/odb/mysql/object-result.txx
@@ -21,6 +21,8 @@ namespace odb
     object_result_impl<T>::
     ~object_result_impl ()
     {
+      if (!this->end_)
+        statement_->free_result ();
     }
 
     template <typename T>
@@ -115,6 +117,9 @@ namespace odb
         this->end_ = count_ > statement_->result_size ();
       else
         fetch ();
+
+      if (this->end_)
+        statement_->free_result ();
     }
 
     template <typename T>
@@ -193,7 +198,10 @@ namespace odb
         statement_->cache ();
 
         if (count_ >= statement_->result_size ())
+        {
+          statement_->free_result ();
           this->end_ = true;
+        }
       }
     }
 
@@ -215,6 +223,8 @@ namespace odb
     object_result_impl_no_id<T>::
     ~object_result_impl_no_id ()
     {
+      if (!this->end_)
+        statement_->free_result ();
     }
 
     template <typename T>
@@ -260,6 +270,9 @@ namespace odb
         this->end_ = count_ > statement_->result_size ();
       else
         fetch ();
+
+      if (this->end_)
+        statement_->free_result ();
     }
 
     template <typename T>
@@ -333,7 +346,10 @@ namespace odb
         statement_->cache ();
 
         if (count_ >= statement_->result_size ())
+        {
+          statement_->free_result ();
           this->end_ = true;
+        }
       }
     }
 
diff --git a/odb/mysql/statement.cxx b/odb/mysql/statement.cxx
index 9278138..6882a27 100644
--- a/odb/mysql/statement.cxx
+++ b/odb/mysql/statement.cxx
@@ -104,16 +104,7 @@ namespace odb
     select_statement::
     ~select_statement ()
     {
-      if (cached_ || conn_.active () == this)
-      {
-        try
-        {
-          free_result ();
-        }
-        catch (...)
-        {
-        }
-      }
+      assert (freed_);
     }
 
     select_statement::
@@ -124,6 +115,7 @@ namespace odb
         : statement (conn, t),
           end_ (false),
           cached_ (false),
+          freed_ (true),
           rows_ (0),
           param_ (&param),
           param_version_ (0),
@@ -141,6 +133,7 @@ namespace odb
         : statement (conn, t, ct),
           end_ (false),
           cached_ (false),
+          freed_ (true),
           rows_ (0),
           param_ (&param),
           param_version_ (0),
@@ -154,6 +147,7 @@ namespace odb
         : statement (conn, t),
           end_ (false),
           cached_ (false),
+          freed_ (true),
           rows_ (0),
           param_ (0),
           result_ (result),
@@ -169,6 +163,7 @@ namespace odb
         : statement (conn, t, ct),
           end_ (false),
           cached_ (false),
+          freed_ (true),
           rows_ (0),
           param_ (0),
           result_ (result),
@@ -179,10 +174,9 @@ namespace odb
     void select_statement::
     execute ()
     {
-      conn_.clear ();
+      assert (freed_);
 
-      if (cached_)
-        free_result ();
+      conn_.clear ();
 
       end_ = false;
       rows_ = 0;
@@ -209,6 +203,7 @@ namespace odb
       if (mysql_stmt_execute (stmt_))
         translate_error (conn_, stmt_);
 
+      freed_ = false;
       conn_.active (this);
     }
 
@@ -306,15 +301,19 @@ namespace odb
     void select_statement::
     free_result ()
     {
-      end_ = true;
-      cached_ = false;
-      rows_ = 0;
+      if (!freed_)
+      {
+        if (mysql_stmt_free_result (stmt_))
+          translate_error (conn_, stmt_);
 
-      if (mysql_stmt_free_result (stmt_))
-        translate_error (conn_, stmt_);
+        if (conn_.active () == this)
+          conn_.active (0);
 
-      if (conn_.active () == this)
-        conn_.active (0);
+        end_ = true;
+        cached_ = false;
+        freed_ = true;
+        rows_ = 0;
+      }
     }
 
     void select_statement::
diff --git a/odb/mysql/statement.hxx b/odb/mysql/statement.hxx
index 9ab95e8..700a7f5 100644
--- a/odb/mysql/statement.hxx
+++ b/odb/mysql/statement.hxx
@@ -146,6 +146,7 @@ namespace odb
     private:
       bool end_;
       bool cached_;
+      bool freed_;
       std::size_t rows_;
       std::size_t size_;
 
@@ -156,6 +157,19 @@ namespace odb
       std::size_t result_version_;
     };
 
+    struct LIBODB_MYSQL_EXPORT auto_result
+    {
+      explicit auto_result (select_statement& s): s_ (s) {}
+      ~auto_result () {s_.free_result ();}
+
+    private:
+      auto_result (const auto_result&);
+      auto_result& operator= (const auto_result&);
+
+    private:
+      select_statement& s_;
+    };
+
     class LIBODB_MYSQL_EXPORT insert_statement: public statement
     {
     public:
diff --git a/odb/mysql/view-result.txx b/odb/mysql/view-result.txx
index 6161909..6f1896d 100644
--- a/odb/mysql/view-result.txx
+++ b/odb/mysql/view-result.txx
@@ -15,6 +15,8 @@ namespace odb
     view_result_impl<T>::
     ~view_result_impl ()
     {
+      if (!this->end_)
+        statement_->free_result ();
     }
 
     template <typename T>
@@ -60,6 +62,9 @@ namespace odb
         this->end_ = count_ > statement_->result_size ();
       else
         fetch ();
+
+      if (this->end_)
+        statement_->free_result ();
     }
 
     template <typename T>
@@ -132,7 +137,10 @@ namespace odb
         statement_->cache ();
 
         if (count_ >= statement_->result_size ())
+        {
+          statement_->free_result ();
           this->end_ = true;
+        }
       }
     }
 
-- 
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