Re: Protocol Question

Thomas Heller <info@zilence.net> writes:
> The first 16 bits (well skip the first 40) in every DataRow ('D') packet
> refer to the number of columns following. Is there any way that this number
> is different from the number received in the RowDescription ('T')?

A quick look into libpq says that it doesn't support them being different:
   /* Get the field count and make sure it's what we expect */   if (pqGetInt(&tupnfields, 2, conn))   {       /* We
shouldnot run out of data here, so complain */       errmsg = libpq_gettext("insufficient data in \"D\" message");
goto advance_and_error;   }
 
   if (tupnfields != nfields)   {       errmsg = libpq_gettext("unexpected field count in \"D\" message");       goto
advance_and_error;  }
 

> Currently I use an assert since I assume it always is the same, however I
> only have tested with a very limited dataset so far.

An assert seems overly optimistic.  libpq has an explicit test with an
error recovery path, you should too.
        regards, tom lane