Implement uniform handle management across all databases

Also use the auto_handle template instead of the raw handle in connection,
statement, and result classes. This removes a lot of brittle "exception
safety guarantee" code that we had in those classes.

9 files changed, 190 insertions, 173 deletions

diff --git a/odb/pgsql/auto-handle.cxx b/odb/pgsql/auto-handle.cxx
new file mode 100644
index 0000000..08e3006
--- /dev/null
+++ b/odb/pgsql/auto-handle.cxx
@@ -0,0 +1,26 @@
+// file      : odb/pgsql/auto-handle.cxx
+// author    : Constantin Michael <constantin@codesynthesis.com>
+// copyright : Copyright (c) 2005-2011 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#include <libpq-fe.h>
+
+#include <odb/pgsql/auto-handle.hxx>
+
+namespace odb
+{
+  namespace pgsql
+  {
+    void handle_traits<PGconn>::
+    release (PGconn* h)
+    {
+      PQfinish (h);
+    }
+
+    void handle_traits<PGresult>::
+    release (PGresult* h)
+    {
+      PQclear (h);
+    }
+  }
+}
diff --git a/odb/pgsql/auto-handle.hxx b/odb/pgsql/auto-handle.hxx
new file mode 100644
index 0000000..2ed58e5
--- /dev/null
+++ b/odb/pgsql/auto-handle.hxx
@@ -0,0 +1,92 @@
+// file      : odb/pgsql/auto-handle.hxx
+// author    : Constantin Michael <constantin@codesynthesis.com>
+// copyright : Copyright (c) 2005-2011 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#ifndef ODB_PGSQL_AUTO_HANDLE_HXX
+#define ODB_PGSQL_AUTO_HANDLE_HXX
+
+#include <odb/pre.hxx>
+
+#include <odb/pgsql/version.hxx>
+#include <odb/pgsql/pgsql-fwd.hxx> // PGconn, PGresult
+
+#include <odb/pgsql/details/export.hxx>
+
+namespace odb
+{
+  namespace pgsql
+  {
+    template <typename H>
+    struct handle_traits;
+
+    template <>
+    struct LIBODB_PGSQL_EXPORT handle_traits<PGconn>
+    {
+      static void
+      release (PGconn*);
+    };
+
+    template <>
+    struct LIBODB_PGSQL_EXPORT handle_traits<PGresult>
+    {
+      static void
+      release (PGresult*);
+    };
+
+    template <typename H>
+    class auto_handle
+    {
+    public:
+      auto_handle (H* h = 0)
+          : h_ (h)
+      {
+      }
+
+      ~auto_handle ()
+      {
+        if (h_ != 0)
+          handle_traits<H>::release (h_);
+      }
+
+      H*
+      get () const
+      {
+        return h_;
+      }
+
+      void
+      reset (H* h = 0)
+      {
+        if (h_ != 0)
+          handle_traits<H>::release (h_);
+
+        h_ = h;
+      }
+
+      H*
+      release ()
+      {
+        H* h (h_);
+        h_ = 0;
+        return h;
+      }
+
+      operator H* ()
+      {
+        return h_;
+      }
+
+    private:
+      auto_handle (const auto_handle&);
+      auto_handle& operator= (const auto_handle&);
+
+    private:
+      H* h_;
+    };
+  }
+}
+
+#include <odb/post.hxx>
+
+#endif // ODB_PGSQL_AUTO_HANDLE_HXX
diff --git a/odb/pgsql/connection.cxx b/odb/pgsql/connection.cxx
index be88446..6f0feaf 100644
--- a/odb/pgsql/connection.cxx
+++ b/odb/pgsql/connection.cxx
@@ -16,7 +16,6 @@
 #include <odb/pgsql/error.hxx>
 #include <odb/pgsql/exceptions.hxx>
 #include <odb/pgsql/statement-cache.hxx>
-#include <odb/pgsql/result-ptr.hxx>
 
 using namespace std;
 
@@ -33,17 +32,12 @@ namespace odb
     connection (database_type& db)
         : odb::connection (db), db_ (db)
     {
-      handle_ = PQconnectdb (db.conninfo ().c_str ());
+      handle_.reset (PQconnectdb (db.conninfo ().c_str ()));
 
       if (handle_ == 0)
         throw bad_alloc ();
       else if (PQstatus (handle_) == CONNECTION_BAD)
-      {
-        std::string m (PQerrorMessage (handle_));
-        PQfinish (handle_);
-
-        throw database_exception (m);
-      }
+        throw database_exception (PQerrorMessage (handle_));
 
       init ();
     }
@@ -77,11 +71,6 @@ namespace odb
     connection::
     ~connection ()
     {
-      // Deallocate prepared statements before we close the connection.
-      //
-      statement_cache_.reset ();
-
-      PQfinish (handle_);
     }
 
     transaction_impl* connection::
@@ -97,8 +86,7 @@ namespace odb
       //
       string str (s, n);
 
-      result_ptr r (PQexec (handle_, str.c_str ()));
-      PGresult* h (r.get ());
+      auto_handle<PGresult> h (PQexec (handle_, str.c_str ()));
 
       unsigned long long count (0);
 
diff --git a/odb/pgsql/connection.hxx b/odb/pgsql/connection.hxx
index 063f8d4..fd74c6e 100644
--- a/odb/pgsql/connection.hxx
+++ b/odb/pgsql/connection.hxx
@@ -19,6 +19,7 @@
 #include <odb/pgsql/version.hxx>
 #include <odb/pgsql/forward.hxx>
 #include <odb/pgsql/transaction-impl.hxx>
+#include <odb/pgsql/auto-handle.hxx>
 #include <odb/pgsql/pgsql-fwd.hxx> // PGconn
 
 #include <odb/pgsql/details/export.hxx>
@@ -84,8 +85,11 @@ namespace odb
 
     private:
       database_type& db_;
-      PGconn* handle_;
+      auto_handle<PGconn> handle_;
 
+      // Keep statement_cache_ after handle_ so that it is destroyed before
+      // the connection is closed.
+      //
       std::auto_ptr<statement_cache_type> statement_cache_;
     };
   }
diff --git a/odb/pgsql/makefile b/odb/pgsql/makefile
index 7e95f24..8203235 100644
--- a/odb/pgsql/makefile
+++ b/odb/pgsql/makefile
@@ -7,6 +7,7 @@
 include $(dir $(lastword $(MAKEFILE_LIST)))../../build/bootstrap.make
 
 cxx :=                    \
+auto-handle.cxx           \
 connection.cxx            \
 connection-factory.cxx    \
 database.cxx              \
diff --git a/odb/pgsql/result-ptr.hxx b/odb/pgsql/result-ptr.hxx
deleted file mode 100644
index 2c5ee89..0000000
--- a/odb/pgsql/result-ptr.hxx
+++ /dev/null
@@ -1,76 +0,0 @@
-// file      : odb/pgsql/result-ptr.hxx
-// author    : Constantin Michael <constantin@codesynthesis.com>
-// copyright : Copyright (c) 2005-2011 Code Synthesis Tools CC
-// license   : GNU GPL v2; see accompanying LICENSE file
-
-#ifndef ODB_PGSQL_RESULT_PTR_HXX
-#define ODB_PGSQL_RESULT_PTR_HXX
-
-#include <odb/pre.hxx>
-
-#include <libpq-fe.h>
-
-#include <odb/pgsql/version.hxx>
-
-#include <odb/pgsql/details/export.hxx>
-
-//
-// Note: do not include this header into public headers (i.e., those
-// that may be included, directly or indirectly, by user code) because
-// it includes libpq-fe.h
-//
-
-namespace odb
-{
-  namespace pgsql
-  {
-    class LIBODB_PGSQL_EXPORT result_ptr
-    {
-    public:
-      result_ptr (PGresult* r = 0)
-          : r_ (r)
-      {
-      }
-
-      ~result_ptr ()
-      {
-        if (r_ != 0)
-          PQclear (r_);
-      }
-
-      PGresult*
-      get () const
-      {
-        return r_;
-      }
-
-      void
-      reset (PGresult* r = 0)
-      {
-        if (r_ != 0)
-          PQclear (r_);
-
-        r_ = r;
-      }
-
-      PGresult*
-      release ()
-      {
-        PGresult* r (r_);
-        r_ = 0;
-        return r;
-      }
-
-    private:
-      result_ptr (const result_ptr&);
-      result_ptr& operator= (const result_ptr&);
-
-    private:
-      PGresult* r_;
-    };
-  }
-}
-
-#include <odb/post.hxx>
-
-#endif // ODB_PGSQL_RESULT_PTR_HXX
diff --git a/odb/pgsql/statement.cxx b/odb/pgsql/statement.cxx
index 26ae475..7e5b5aa 100644
--- a/odb/pgsql/statement.cxx
+++ b/odb/pgsql/statement.cxx
@@ -14,7 +14,7 @@
 #include <odb/pgsql/statement.hxx>
 #include <odb/pgsql/connection.hxx>
 #include <odb/pgsql/transaction.hxx>
-#include <odb/pgsql/result-ptr.hxx>
+#include <odb/pgsql/auto-handle.hxx>
 #include <odb/pgsql/error.hxx>
 
 #include <odb/pgsql/details/endian-traits.hxx>
@@ -53,7 +53,7 @@ namespace odb
       s += name_;
       s += "\"";
 
-      result_ptr r (PQexec (conn_.handle (), s.c_str ()));
+      auto_handle<PGresult> h (PQexec (conn_.handle (), s.c_str ()));
       deallocated_ = true;
     }
 
@@ -67,14 +67,20 @@ namespace odb
           name_ (name),
           deallocated_ (false)
     {
-      result_ptr r (PQprepare (conn_.handle (),
-                               name_.c_str (),
-                               stmt.c_str (),
-                               static_cast<int> (types_count),
-                               types));
-
-      if (!is_good_result (r.get ()))
-        translate_error (conn_, r.get ());
+      auto_handle<PGresult> h (
+        PQprepare (conn_.handle (),
+                   name_.c_str (),
+                   stmt.c_str (),
+                   static_cast<int> (types_count),
+                   types));
+
+      if (!is_good_result (h))
+        translate_error (conn_, h);
+
+      //
+      // If any code after this line throws, the statement will be leaked
+      // (on the server) since deallocate() won't be called for it.
+      //
     }
 
     void statement::
@@ -295,8 +301,6 @@ namespace odb
     select_statement::
     ~select_statement ()
     {
-      if (result_ != 0)
-        PQclear (result_);
     }
 
     select_statement::
@@ -312,10 +316,8 @@ namespace odb
           cond_ (&cond),
           native_cond_ (native_cond),
           data_ (data),
-          result_ (0),
           row_count_ (0),
           current_row_ (0)
-
     {
     }
 
@@ -331,55 +333,39 @@ namespace odb
           cond_ (0),
           native_cond_ (native_cond),
           data_ (data),
-          result_ (0),
           row_count_ (0),
           current_row_ (0)
-
     {
     }
 
     void select_statement::
     execute ()
     {
-      if (result_ != 0)
-      {
-        PQclear (result_);
-        result_ = 0;
-      }
+      result_.reset ();
 
       if (cond_ != 0)
         bind_param (native_cond_, *cond_);
 
-      // Use temporary result_ptr to guarantee exception safety.
-      //
-      result_ptr r (PQexecPrepared (conn_.handle (),
-                                    name_.c_str (),
-                                    native_cond_.count,
-                                    native_cond_.values,
-                                    native_cond_.lengths,
-                                    native_cond_.formats,
-                                    1));
+      result_.reset (
+        PQexecPrepared (conn_.handle (),
+                        name_.c_str (),
+                        native_cond_.count,
+                        native_cond_.values,
+                        native_cond_.lengths,
+                        native_cond_.formats,
+                        1));
 
-      PGresult* h (r.get ());
+      if (!is_good_result (result_))
+        translate_error (conn_, result_);
 
-      if (!is_good_result (h))
-        translate_error (conn_, h);
-
-      row_count_ = static_cast<size_t> (PQntuples (h));
+      row_count_ = static_cast<size_t> (PQntuples (result_));
       current_row_ = 0;
-
-      result_ = r.release ();
     }
 
     void select_statement::
     free_result ()
     {
-      if (result_ != 0)
-      {
-        PQclear (result_);
-        result_ = 0;
-      }
-
+      result_.reset ();
       row_count_ = 0;
       current_row_ = 0;
     }
@@ -450,14 +436,15 @@ namespace odb
 
       bind_param (native_data_, data_);
 
-      result_ptr r (PQexecPrepared (conn_.handle (),
-                                    name_.c_str (),
-                                    native_data_.count,
-                                    native_data_.values,
-                                    native_data_.lengths,
-                                    native_data_.formats,
-                                    1));
-      PGresult* h (r.get ());
+      auto_handle<PGresult> h (
+        PQexecPrepared (conn_.handle (),
+                        name_.c_str (),
+                        native_data_.count,
+                        native_data_.values,
+                        native_data_.lengths,
+                        native_data_.formats,
+                        1));
+
       ExecStatusType stat (PGRES_FATAL_ERROR);
 
       if (!is_good_result (h, &stat))
@@ -482,10 +469,8 @@ namespace odb
       if (id_cached_)
         return id_;
 
-      result_ptr r (PQexecParams (conn_.handle (),
-                                  "select lastval ()",
-                                  0, 0, 0, 0, 0, 1));
-      PGresult* h (r.get ());
+      auto_handle<PGresult> h (
+        PQexecParams (conn_.handle (), "select lastval ()", 0, 0, 0, 0, 0, 1));
 
       if (!is_good_result (h))
         translate_error (conn_, h);
@@ -534,15 +519,14 @@ namespace odb
       bind_param (native_data_, data_);
       bind_param (native_cond_, cond_);
 
-      result_ptr r (PQexecPrepared (conn_.handle (),
-                                    name_.c_str (),
-                                    native_data_.count + native_cond_.count,
-                                    native_data_.values,
-                                    native_data_.lengths,
-                                    native_data_.formats,
-                                    1));
-
-      PGresult* h (r.get ());
+      auto_handle<PGresult> h (
+        PQexecPrepared (conn_.handle (),
+                        name_.c_str (),
+                        native_data_.count + native_cond_.count,
+                        native_data_.values,
+                        native_data_.lengths,
+                        native_data_.formats,
+                        1));
 
       if (!is_good_result (h))
         translate_error (conn_, h);
@@ -596,14 +580,14 @@ namespace odb
       if (cond_ != 0)
         bind_param (native_cond_, *cond_);
 
-      result_ptr r (PQexecPrepared (conn_.handle (),
-                                    name_.c_str (),
-                                    native_cond_.count,
-                                    native_cond_.values,
-                                    native_cond_.lengths,
-                                    native_cond_.formats,
-                                    1));
-      PGresult* h (r.get ());
+      auto_handle<PGresult> h (
+        PQexecPrepared (conn_.handle (),
+                        name_.c_str (),
+                        native_cond_.count,
+                        native_cond_.values,
+                        native_cond_.lengths,
+                        native_cond_.formats,
+                        1));
 
       if (!is_good_result (h))
         translate_error (conn_, h);
diff --git a/odb/pgsql/statement.hxx b/odb/pgsql/statement.hxx
index 11e04b3..6e5484a 100644
--- a/odb/pgsql/statement.hxx
+++ b/odb/pgsql/statement.hxx
@@ -15,7 +15,8 @@
 
 #include <odb/pgsql/version.hxx>
 #include <odb/pgsql/binding.hxx>
-#include <odb/pgsql/pgsql-fwd.hxx>
+#include <odb/pgsql/pgsql-fwd.hxx> // PGresult
+#include <odb/pgsql/auto-handle.hxx>
 
 #include <odb/pgsql/details/export.hxx>
 
@@ -157,7 +158,7 @@ namespace odb
 
       binding& data_;
 
-      PGresult* result_;
+      auto_handle<PGresult> result_;
       std::size_t row_count_;
       std::size_t current_row_;
     };
diff --git a/odb/pgsql/transaction-impl.cxx b/odb/pgsql/transaction-impl.cxx
index c3ce31d..e4604e3 100644
--- a/odb/pgsql/transaction-impl.cxx
+++ b/odb/pgsql/transaction-impl.cxx
@@ -12,7 +12,7 @@
 #include <odb/pgsql/error.hxx>
 #include <odb/pgsql/exceptions.hxx>
 #include <odb/pgsql/transaction-impl.hxx>
-#include <odb/pgsql/result-ptr.hxx>
+#include <odb/pgsql/auto-handle.hxx>
 
 namespace odb
 {
@@ -46,8 +46,7 @@ namespace odb
         odb::transaction_impl::connection_ = connection_.get ();
       }
 
-      result_ptr r (PQexec (connection_->handle (), "begin"));
-      PGresult* h (r.get ());
+      auto_handle<PGresult> h (PQexec (connection_->handle (), "begin"));
 
       if (!h || PGRES_COMMAND_OK != PQresultStatus (h))
         translate_error (*connection_, h);
@@ -56,8 +55,7 @@ namespace odb
     void transaction_impl::
     commit ()
     {
-      result_ptr r (PQexec (connection_->handle (), "commit"));
-      PGresult* h (r.get ());
+      auto_handle<PGresult> h (PQexec (connection_->handle (), "commit"));
 
       if (!h || PGRES_COMMAND_OK != PQresultStatus (h))
         translate_error (*connection_, h);
@@ -66,8 +64,7 @@ namespace odb
     void transaction_impl::
     rollback ()
     {
-      result_ptr r (PQexec (connection_->handle (), "rollback"));
-      PGresult* h (r.get ());
+      auto_handle<PGresult> h (PQexec (connection_->handle (), "rollback"));
 
       if (!h || PGRES_COMMAND_OK != PQresultStatus (h))
         translate_error (*connection_, h);