Re: logical decoding : exceeded maxAllocatedDescs for .spill files

On Wed, 20 Nov 2019 at 01:05, Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
>
> On Wed, Nov 20, 2019 at 7:58 AM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> > On Wed, Nov 20, 2019 at 1:14 AM Juan José Santamaría Flecha
> > > https://devblogs.microsoft.com/oldnewthing/20150121-00/?p=44863
> >
> > !?!

Thanks Juan and Thomas for pointing to these links where already this
was discussed.

>
> One thing I don't understand (besides, apparently, the documentation):
> how did this problem escape detection by check-world for such a long
> time? Surely we expect to hit the end of various temporary files in
> various tests. Is it intermittent, or dependent on Windows version,
> or something like that?

Possibly there aren't any callers who try to pread() at end-of-file
using FileRead/pg_pread :

- mdread() seems to read from an offset which it seems to know that it
is inside the end-of file, including the whole BLCKSZ.
- BufFileLoadBuffer() seems to deliberately ignore FileRead()'s return
value if it is -1
if (file->nbytes < 0) file->nbytes = 0;
- XLogPageRead() also seems to know that the offset is a valid offset.

--
Thanks,
-Amit Khandekar
EnterpriseDB Corporation
The Postgres Database Company