Re: 回复：[Internet]Re: [PATCH] Prevent replacement of a function if it's used in an index expression and is not IMMUTABLE
| От | David G. Johnston |
|---|---|
| Тема | Re: 回复：[Internet]Re: [PATCH] Prevent replacement of a function if it's used in an index expression and is not IMMUTABLE |
| Дата | |
| Msg-id | CAKFQuwZD+V-9Tm8OD2Zx6hgvU=f8aQ+xjaD7EhP7OLvc=ZF8BQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: 回复：[Internet]Re: [PATCH] Prevent replacement of a function if it's used in an index expression and is not IMMUTABLE (Tom Lane <tgl@sss.pgh.pa.us>) |
| Ответы |
Re: 回复：[Internet]Re: [PATCH] Prevent replacement of a function if it's used in an index expression and is not IMMUTABLE
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| Список | pgsql-hackers |
On Wed, Jul 9, 2025 at 9:15 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
"sundayjiang(蒋浩天)" <sundayjiang@tencent.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.
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