Re: 回复：[Internet]Re: [PATCH] Prevent replacement of a function if it's used in an index expression and is not IMMUTABLE

On Wed, Jul 9, 2025 at 9:15 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "=?utf-8?B?c3VuZGF5amlhbmco6JKL5rWp5aSpKQ==?=" <sundayjiang(at)tencent(dot)com>
> writes:
> > > The purpose of this patch is to prevent replacing a function via
> `CREATE OR REPLACE FUNCTION` with a new definition that is not marked as
> `IMMUTABLE`, if the existing function is referenced by an index expression.
> > >
> > > Replacing such functions may lead to index corruption or runtime
> semantic inconsistencies, especially when the function’s output is not
> stable for the same input.
>
>
> TBH, I find this proposal to be useless nannyism. Replacing a
> function that is used in an index is problematic if you change its
> behavior (that is, its actual output for given inputs) in any way.
> Whether it's marked IMMUTABLE is a very minor side point.
>

Isn't preventing a dump-restore hazard sufficient reason to do this? The
now-volatile function will be dumped as such and the create index during
the restore will fail because of that.

David J.