Re: Move SLRU_PAGES_PER_SEGMENT to pg_config_manual.h

On 10/11/2025 19:46, Heikki Linnakangas wrote:
> Fixed. And I just noticed another thing I forgot: pg_resetwal and 
> pg_controldata.

Fixed that.

> While testing, I noticed that pg_controldata doesn't check 
> PG_CONTROL_VERSION. If you add a field to ControlFileData that changes 
> the length, you'll get a warning that the CRC doesn't match:
> 
>> pg_controldata: warning: calculated CRC checksum does not match value 
>> stored in control file
>> pg_controldata: detail: Either the control file is corrupt, or it has 
>> a different layout than this program is expecting.  The results below 
>> are untrustworthy.
> 
> but if you make any changes that *don't* change ControlFileData's size, 
> pg_controldata will merrily try to interpret the values with no warning. 
> Surely it should also check PG_CONTROL_VERSION?

Committed an additional version check to pg_controldata. It now gives a 
a more explicit warning than just checksum failure if the version in the 
control file doesn't match the PG_CONTROL_VERSION that the binary was 
built with:

> ~/git-sandbox-pgsql/master$ ./src/bin/pg_controldata/pg_controldata -D ~/pgsql.18stable/data
> pg_controldata: warning: control file version (1800) does not match the version understood by this program (1900)
> pg_controldata: detail: Either the control file has been created with a different version of PostgreSQL, or it is corrupt.  The results below are untrustworthy.
> pg_controldata: warning: invalid WAL segment size in control file (64 bytes)
> pg_controldata: detail: The WAL segment size must be a power of two between 1 MB and 1 GB.
> pg_controldata: detail: The file is corrupt and the results below are untrustworthy.
> pg_control version number:            1800
> Catalog version number:               202506291
> Database system identifier:           7571514922284774749
> Database cluster state:               shut down
> pg_control last modified:             Tue 11 Nov 2025 19:04:53 EET
> ...

- Heikki