Thread

RE: doc: update the default of data checksums in the doc of pg_rewind

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com> — 2025-12-25T03:14:19Z

On Thursday, December 25, 2025 8:22 AM Chao Li <li.evan.chao@gmail.com> wrote:
> 
> > On Dec 24, 2025, at 15:27, Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>
> wrote:
> >
> > Hi,
> >
> > I noticed that the pg_rewind documentation still states that data
> > checksums is disabled by default, but it has been changed to on since PG18.
> >
> > Here's a small patch to update this.
> >
> > Best Regards,
> > Hou zj
> > <v1-0001-Fix-outdated-doc-in-pg_rewind.patch>
> 
> 
> ```
> -   the cluster was initialized with <application>initdb</application>.  Neither
> of these
> -   are currently on by default.  <xref linkend="guc-full-page-writes"/>
> -   must also be set to <literal>on</literal>, but is enabled by default.
> +   the cluster was initialized with <application>initdb</application> (the
> latter
> +   being the default).  <xref linkend="guc-full-page-writes"/> must also be set
> +   to <literal>on</literal>, but is enabled by default.
> ```
> 
> I think we can explicitly mention PG18 and later, like:
> ```
> the cluster was initialized with <application>initdb</application> (data
> checksums are enabled by default in PostgreSQL 18 and later).
> ```
> 
> I searched over the docs, the usage of “<version> and later” is not rare, for
> example:
> ```
>   <para>
>    <application>pg_amcheck</application> is designed to work with
>    <productname>PostgreSQL</productname> 14.0 and later.
>   </para>
> ```

I think including a version number here is necessary, as pg_rewind is not compatible
with older PostgreSQL versions. It should be the release notes of PostgreSQL 18
to reflect changes in default values, rather than the pg_rewind doc mentioning
a behavior change. (We don't mention version number in initdb's doc as well)

Best Regards,
Hou zj