Re: BUG #3855: backend sends corrupted data onEHOSTDOWNerror

Email removed from patch queue --- Tom indicates this is an operating
system bug.  Perhaps if we get more bug reports we will have to address
it.

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

Scot Loach wrote:
> Yes that is what I am trying to explain.
> So I think this is still a bug that should be fixed in the backend code.
>
> scot.
>
>
> -----Original Message-----
> From: Jeff Davis [mailto:pgsql@j-davis.com]
> Sent: Tuesday, January 08, 2008 2:40 PM
> To: Scot Loach
> Cc: pgsql-bugs@postgresql.org
> Subject: RE: [BUGS] BUG #3855: backend sends corrupted data
> onEHOSTDOWNerror
>
> On Tue, 2008-01-08 at 14:06 -0500, Scot Loach wrote:
> > I agree this would be fine if PostgreSQL works the way you say below.
> >
> > However, PostgreSQL does not look at the # of bytes written and
> > continue sending after that many bytes.  PostgreSQL actually simply
> > clears its buffer of bytes to send on this error, in this code:
> >
> > pqcomm.c:1075
> >         /*
> >          * We drop the buffered data anyway so that processing can
> >          * continue, even though we'll probably quit soon.
> >          */
> >         PqSendPointer = 0;
> >         return EOF;
> >
> >
> > The result as I saw on a system where this was occurring, was that
> > when PostgreSQL was sending back a large result set, there was simply
> > a fragment of it missing.
>
> I think I see what you are saying. I was thinking about fe-misc.c, where
> it explicitly says (in the default case of a switch statement of the
> return value):
>
> /* We don't assume it's a fatal error... */
> conn->outCount = 0;
> return -1;
>
> (but that's on the frontend, obviously)
>
> I think the problem you're talking about comes from the callers of
> pq_putmessage, which simply ignore any return value at all (and thus do
> not retransmit the message). I agree that is a problem (assuming I
> understand what's going on).
>
> Regards,
>     Jeff Davis
>
>
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  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://postgres.enterprisedb.com

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