Re: BufFileWrite across MAX_PHYSICAL_FILESIZE boundary

I wrote:
> "Kurt Harriman" <kharriman@greenplum.com> writes:
>> Just noticed buffile.c:292 doesn't look quite right where
>> BufFileDumpBuffer calls FileWrite:
>> bytestowrite = FileWrite(thisfile, file->buffer, bytestowrite);
>> It looks as though it would write the same data each time the
>> loop is iterated.  Would this be better?
>> bytestowrite = FileWrite(thisfile, file->buffer + wpos, bytestowrite);

> Yeah, I think you're right.

FYI, I was able to exercise the bug by changing RELSEG_SIZE to 2 within
buffile.c and then running this script in the regression database:

set work_mem = '64kB';
begin;
declare c scroll cursor for select * from tenk1 a join tenk1 b using(two);
fetch 1 from c;
fetch 100 from c;
fetch backward 10 from c;
fetch 100 from c;
fetch backward 10 from c;
fetch 100 from c;
fetch backward 100 from c;
commit;

It doesn't crash with the fix applied.  Thanks for spotting it.
        regards, tom lane