Horton

Re: Add a GUC check hook to ensure summarize_wal cannot be enabled when wal_level is minimal

Robert Haas <robertmhaas@gmail.com>

View thread View on postgr.es
From: Robert Haas <robertmhaas@gmail.com>
To: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2024-07-03T19:13:37Z
Lists: pgsql-hackers 
On Wed, Jul 3, 2024 at 10:09 AM Fujii Masao <masao.fujii@oss.nttdata.com> wrote:
> The documentation states that "WAL summarization cannot be enabled when wal_level is set to minimal." Therefore, at startup, the postmaster checks these settings and exits with an error if they are not configured properly.
>
> However, I found that summarize_wal can still be enabled while the server is running with wal_level=minimal. Please see the following example to cause this situation. I think this is a bug.

Well, that's unfortunate. I suppose I got confused about whether
summarize_wal could be changed without a server restart.

I think the fix is probably not to cross-check the GUC values, but to
put something in the summarizer that prevents it from generating a
summary file if wal_level==minimal. Because an incremental backup
based on such summaries would be no good. I won't be working the next
couple of days due to the US holiday tomorrow, but I've made a note to
look into this more next week.

-- 
Robert Haas
EDB: http://www.enterprisedb.com

Commits

  1. Do not summarize WAL if generated with wal_level=minimal.

  2. Revert "Auto-tune effective_cache size to be 4x shared buffers"

  3. Un-break ecpg test suite under --disable-integer-datetimes.

  4. Again fix initialization of auto-tuned effective_cache_size.

  5. Code review for auto-tuned effective_cache_size.

  6. Auto-tune effective_cache size to be 4x shared buffers