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Re: [ODBC] RE: [PATCHES] Fix for ODBC close

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org>
Cc: Dave Page <dpage(at)vale-housing(dot)co(dot)uk>, PostgreSQL odbc list <pgsql-odbc(at)postgreSQL(dot)org>, PostgreSQL-patches <pgsql-patches(at)postgreSQL(dot)org>
Subject: Re: [ODBC] RE: [PATCHES] Fix for ODBC close
Date: 2001-02-11 06:30:57
Message-ID: 200102110630.BAA20038@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-odbcpgsql-patches
OK, I have a pretty good guess about the cause of the ODBC shutdown
failure message in the server logs.  Sending 'X' is still causing the
error message.

The error you are seeing is from the backend libpq code, the area that
communicates with clients.

So, let's assume the problem is not the platform, but the client code. 
Libpq properly shuts connections without triggering that message.  ODBC
does trigger the message.

libpq closes connections with:

		(void) pqPuts("X", conn);
		(void) pqFlush(conn);

while ODBC closes with:

		SOCK_put_char(self, 'X');
		SOCK_flush_output(self);

They then close() the socket.

It seems the difference is in the flushing.  libpq has elaborate flush
code:

	while (len > 0)
	{
			sent = send(conn->sock, ptr, len, 0);
			len -= sent;

			if (pqWait(FALSE, TRUE, conn))
	}

and pqWait does:

		if (select(conn->sock + 1, &input_mask, &output_mask, (fd_set *) NULL,


For flush, ODBC does a simple:

	written = send(self->socket, (char *) self->buffer_out, self->buffer_filled_out, 0);


It seems we may need to add flush code similar to libpq in ODBC.

At a minimum, we have to put the send() in a loop and keep going until
there are no more bytes to send.  Not sure the select() is required.

Comments?

After I receive comments, I will prepare a patch people can test.


---------------------------------------------------------------------------



.  > OK, I have ifdef'ed out the sending of the 'X' parameter.  I will see if
> placing it somewhere else will help.  Could it have to do with the fact
> we are in a transaction in ODBC?  My guess is that the X is returning
> data that is triggering the error.
> 
> [ Charset ISO-8859-1 unsupported, converting... ]
> > 
> > 
> > > -----Original Message-----
> > > From: Bruce Momjian [mailto:pgman(at)candle(dot)pha(dot)pa(dot)us]
> > > Sent: 10 February 2001 05:46
> > > To: PostgreSQL odbc list; PostgreSQL-patches
> > > Cc: PostgreSQL-development
> > > Subject: [PATCHES] Fix for ODBC close
> > > 
> > > 
> > > I have applied the following patch to properly exit ODBC. 
> > 
> > <Snip>
> > 
> > I just compiled from the current cvs under win32 and I still get
> > 'pq_recvbuf: unexpected EOF on client connection' when exiting apps using
> > the ODBC driver. I have tested with pgAdmin which uses ADO (ActiveX Data
> > Objects) and certainly closes the ADO connection object on exit, as well as
> > a simple test app using DAO (Data Access Objects). I did have a go at fixing
> > this myself when Bruce first mentioned it, and had exactly the same results
> > with similar code :-(
> > 
> > Regards, 
> > 
> > Dave.
> > 
> 
> 
> -- 
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
>   +  If your life is a hard drive,     |  830 Blythe Avenue
>   +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026
> 


-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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