Re: [PATCH] pg_upgrade: add --initdb option to create the new cluster automatically

> On 17 Jul 2026, at 14:10, Bohyun Lee <bohyun(dot)lee(at)databricks(dot)com> wrote:

> • Reworked the manual-initdb docs: the vague "use compatible initdb flags" is now the specific settings that must match (WAL segment size, checksums, encoding, locale), with a pointer to pg_controldata.

Regardless of the rest of the patch, I think we should apply something like
this to the docs. I propose you extract this portion into a separate 0001 in
this patchset so that it can be considered individually.

I haven't had a chance to look at the new version more than at skim-level but
the below caught my eye.

+ initPQExpBuffer(&cmd);
+ appendPQExpBuffer(&cmd, "\"%s/initdb\" -D \"%s\" -N",
+ new_cluster.bindir, new_cluster.pgdata);
+ appendPQExpBuffer(&cmd, " -U \"%s\"", os_info.user);

This will inject the username specified in the (untrusted input) commandline
into the initdb command and execute it. While that will work in benign cases,
it seems like a Booby Tables pattern which is best left in the coding practices
of the past and in XKCD?

--
Daniel Gustafsson