From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200102281714.MAA02741@candle.pha.pa.us>
Subject: Re: libpq++: suggested patches for PgTransaction
In-Reply-To: <20010228135500.C20079@cistron.nl> "from J. T. Vermeulen at Feb
	28, 2001 01:55:00 pm"
To: "J. T. Vermeulen" <jtv@cistron-office.nl>
Date: Wed, 28 Feb 2001 12:14:54 -0500 (EST)
CC: pgsql-interfaces@postgresql.org
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I will keep this for 7.2.  Thanks.

> 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
> 
> 


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