Horton

Re: BUG #19520: PANIC when concurrently manipulating stored procedures with pg_stat_statements and track_functions =

Lukas Fittl <lukas@fittl.com>

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From: Lukas Fittl <lukas@fittl.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Álvaro Herrera <alvherre@kurilemu.de>, Ayush Tiwari <ayushtiwari.slg01@gmail.com>, Sami Imseih <samimseih@gmail.com>, zlh21343@163.com, pgsql-bugs@lists.postgresql.org, Andres Freund <andres@anarazel.de>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: 2026-06-20T16:45:05Z
Lists: pgsql-bugs 
On Sat, Jun 20, 2026 at 5:16 AM Michael Paquier <michael@paquier.xyz> wrote:
>
> On Sat, Jun 20, 2026 at 01:09:59PM +0200, Alvaro Herrera wrote:
> > I think a better answer is to just not introduce the ABI change in
> > stable branches.  That is, I think we should add a shim function so that
> > the third-party extensions can continue to use the original ABI; and
> > only in master you clean that up with a different API, whereby the
> > extension will be forced to have an #ifdef block for the 19 version or
> > the older versions, but that's fine because the extension has to be
> > recompiled for the new major version anyway so the end-user won't be
> > affected on a minor upgrade.
>
> If you feel strongly about it, we could just do something like the
> attached in the v15-v18 range.  This introduces a new routine called
> pgstat_drop_entry_ext() that gains the new argument "missing_ok", and
> pgstat_drop_entry() would be an ABI-compatible wrapper calling it.
>
> What do you think?

As the developer of the extension in the picture, I was actually
surprised to see the commit making an ABI *and* API breaking change
(and I think with cumulative stats being pluggable in 18, we can
expect people to use public stats functions like pgstat_drop_entry in
extensions), precisely because of the issues Alvaro mentioned.

I think doing it with a new routine is what I would have expected to
happen to preserve API and ABI compatibility, and your follow-up patch
looks good to me.

Thanks,
Lukas


--
Lukas Fittl

Commits

  1. Re-introduce pgstat_drop_entry(), keeping ABI compatibility

  2. Update .abi-compliance-history for pgstat_drop_entry()

  3. Fix PANIC with track_functions due to concurrent drop of pgstats entries