Re: BUG #17928: Standby fails to decode WAL on termination of primary

Thomas Munro <thomas.munro@gmail.com>

From: Thomas Munro <thomas.munro@gmail.com>

To: Alexander Lakhin <exclusion@gmail.com>

Cc: Michael Paquier <michael@paquier.xyz>, Sergei Kornilov <sk@zsrv.org>, Noah Misch <noah@leadboat.com>, Tom Lane <tgl@sss.pgh.pa.us>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, pgsql-bugs@lists.postgresql.org, Fujii Masao <masao.fujii@oss.nttdata.com>

Date: 2023-09-17T20:46:17Z

Lists: pgsql-bugs

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Correct assertion and comments about XLogRecordMaxSize.
- e1f95ec8cf6e 17.0 landed
Fix edge-case for xl_tot_len broken by bae868ca.
- bde2f1847f51 12.17 landed
- 45d1fe8b53d4 13.13 landed
- 3d413c5a76fa 14.10 landed
- 99d334a187ae 15.5 landed
- 10d0591ea227 16.1 landed
- becfbdd6c1c9 17.0 landed
Don't use Perl pack('Q') in 039_end_of_wal.pl.
- 82314dbfca7f 12.17 landed
- 07896f468f23 13.13 landed
- afa504ba2f5d 14.10 landed
- 21b4c3ca0b22 15.5 landed
- cc58607b019a 16.1 landed
- 91b0e85aa0ad 17.0 landed
Don't trust unvalidated xl_tot_len.
- e8f3c0687116 12.17 landed
- 6606c57162cb 13.13 landed
- 3ce3b53d76a3 14.10 landed
- f4d152edd8f3 15.5 landed
- ce497f648e2d 16.1 landed
- bae868caf222 17.0 landed
Make recovery report error message when invalid page header is found.
- 7b03d3a3ba45 12.17 landed
- 5dc093eacef1 13.13 landed
- 2f13e8d9ec28 14.10 landed
Add more protections in WAL record APIs against overflows
- 8fcb32db98ed 16.0 cited

On Sat, Sep 16, 2023 at 6:00 PM Alexander Lakhin <exclusion@gmail.com> wrote:
> It looks like the construction "@{^CAPTURE}" used in scan_server_header()
> is not supported by Perl 5.24, which is included in Debian stretch:
> https://perldoc.perl.org/variables/@%7B%5ECAPTURE%7D
> I replaced it with
> @match = ($1);
> and that worked for me.

Thanks for catching that!  I see that %{^CAPTURE} was added to Perl
5.25.7, but we document Perl 5.14 or later as the requirement
currently, and for REL_12_STABLE it's Perl 5.8.3.  That would
certainly have turned a few build farm fossils red.

Your replacement only returns the first captured group.  I don't know
Perl, but I think we can just assign the whole array to @match
directly, to maintain the semantics that Michael wanted, like so:

-               if ($line =~ /^$regexp/)
+               if (@match = $line =~ /^$regexp/)
                {
-                       # Found match, so store all the results.
-                       @match = @{^CAPTURE};
                        last;
                }

Better Perl welcome.

Looking into your observation about wal_log_hints...