From: "J. T. Vermeulen" <jtv@cistron-office.nl>
Date: Wed, 28 Feb 2001 13:55:00 +0100
To: pgsql-interfaces@postgresql.org
Subject: libpq++: suggested patches for PgTransaction
Message-ID: <20010228135500.C20079@cistron.nl>
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The original PgTransaction, apparently having been written without exceptions
in mind, didn't know how to abort a transaction.  The suggested change makes
it abort if the transaction object is destroyed without an explicit commit,
as would happen if the program fell out of the transaction code through an
unhandled exception (plus the patch makes constructors explicit where 
appropriate).

Actually this still isn't very effective; I think it would be more useful to
have a separate transaction object "latch onto" an existing connection and
represent a single transaction delimited by the object's entire lifetime.
That would make it easier to perform multiple independent (but presumably
non-overlapping) transactions over the lifetime of a single connection in 
an exception-safe manner.


--- postgresql-7.0.3/src/interfaces/libpq++/pgtransdb.cc	Sun May 30 17:17:58 1999
+++ postgresql-7.0.3-jtv/src/interfaces/libpq++/pgtransdb.cc	Wed Feb 28 13:34:20 2001
@@ -25,7 +25,8 @@
 // Make a connection to the specified database with default environment
 // See PQconnectdb() for conninfo usage. 
 PgTransaction::PgTransaction(const char* conninfo)
-   : PgDatabase(conninfo)
+   : PgDatabase(conninfo),
+     pgCommitted(true)
 {
 	BeginTransaction();
 }
@@ -33,17 +34,20 @@
 // Destructor: End the transaction block
 PgTransaction::~PgTransaction()
 {
-	EndTransaction();
+	if (!pgCommitted) Exec("ABORT");
 }
 
 // Begin the transaction block
 ExecStatusType PgTransaction::BeginTransaction()
 {
+        pgCommitted = false;
 	return Exec("BEGIN");
 } // End BeginTransaction()
 
 // Begin the transaction block
 ExecStatusType PgTransaction::EndTransaction()
 {
+        pgCommitted = true;
 	return Exec("END");
 } // End EndTransaction()
+


--- postgresql-7.0.3/src/interfaces/libpq++/pgtransdb.h	Sun Apr 23 00:39:15 2000
+++ postgresql-7.0.3-jtv/src/interfaces/libpq++/pgtransdb.h	Wed Feb 28 13:34:42 2001
@@ -36,9 +36,9 @@
 // the object is destroyed.
 class PgTransaction : public PgDatabase {
 public:
-  PgTransaction(const char* conninfo);	// use reasonable & environment defaults
+  explicit PgTransaction(const char conninfo[]);	// use reasonable & environment defaults
   // connect to the database with given environment and database name
-  // PgTransaction(const PgConnection&);
+  // explicit PgTransaction(const PgConnection&);
   ~PgTransaction();	// close connection and clean up
   
 protected:
@@ -46,9 +46,11 @@
   ExecStatusType EndTransaction();
   
 protected:
-  PgTransaction() : PgDatabase() {}	// Do not connect
+  PgTransaction() : PgDatabase(), pgCommitted(true) {}	// Do not connect
 
 private:
+  bool pgCommitted;
+
 // We don't support copying of PgTransaction objects,
 // so make copy constructor and assignment op private.
    PgTransaction(const PgTransaction&);


Jeroen