Re: logical decoding : exceeded maxAllocatedDescs for .spill files

On Wed, Nov 20, 2019 at 1:14 AM Juan José Santamaría Flecha
<juanjo(dot)santamaria(at)gmail(dot)com> wrote:
> On Tue, Nov 19, 2019 at 12:49 PM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
>> On Wed, Nov 20, 2019 at 12:28 AM Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com> wrote:
>> > On Windows, it is documented that ReadFile() (which is called by
>> > pg_pread) will return false on EOF but only when the file is open for
>> > asynchronous reads/writes. But here we are just dealing with usual
>> > synchronous reads. So pg_pread() code should indeed return 0 on EOF on
>> > Windows. Not yet able to figure out how FileRead() managed to return
>> > this error on Windows. But from your symptoms, it does look like
>> > pg_pread()=>ReadFile() returned false (despite doing asynchronous
>> > reads), and so _dosmaperr() gets called, and then it does not find the
>> > eof error in doserrors[], so the "unrecognized win32 error code"
>> > message is printed. May have to dig up more on this.
>>
>> Hmm. See also this report:
>>
>> https://www.postgresql.org/message-id/flat/CABuU89MfEvJE%3DWif%2BHk7SCqjSOF4rhgwJWW6aR3hjojpGqFbjQ%40mail.gmail.com
>>
>
> The files from pgwin32_open() are open for synchronous access, while pg_pread() uses the asynchronous functionality to offset the read. Under these circunstances, a read past EOF will return ERROR_HANDLE_EOF (38), as explained in:

Oh, thanks.

> https://devblogs.microsoft.com/oldnewthing/20150121-00/?p=44863

!?!

Amit, since it looks like you are Windows-enabled and have a repro,
would you mind confirming that this fixes the problem?

--- a/src/port/pread.c
+++ b/src/port/pread.c
@@ -41,6 +41,9 @@ pg_pread(int fd, void *buf, size_t size, off_t offset)
overlapped.Offset = offset;
if (!ReadFile(handle, buf, size, &result, &overlapped))
{
+ if (GetLastError() == ERROR_HANDLE_EOF)
+ return 0;
+
_dosmaperr(GetLastError());
return -1;
}