Thread

Re: Segfault due to NULL ParamExecData value

Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com> — 2025-12-05T13:33:26Z

On Thu, Dec 4, 2025 at 4:35 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

> I'm not volunteering to look into this without a reproducer.

However, seeing that EvalPlanQual is in the stack trace,
> my gut feeling is that the EPQ mechanism is somehow mis-managing
> output Params for InitPlans.  I vaguely recall some definitional
> issues around whether it'd be okay to pass down already-computed
> InitPlan results into the EPQ sub-evaluation, or whether we should
> force the sub-evaluation to do those afresh.  It was awhile back
> and I don't remember what was decided.
>

That sounds like an interesting lead. The impacted cluster definitely had a
lot of long transactions updating the same rows with the occasional
deadlocks.

Don't suppose you can try to reproduce this on something newer
> than 14.17?
>

That would be hard. On the production cluster, we've stopped the segfaults
by rewriting the query (faster execution time, so less recheck and EPQ?)
and I don't have much leeway to experiment on those.

I'm currently working on a backup of the cluster trying to redo the same
queries using 14.17, since the issue was happening with this version. If I
manage to have a reproducer, I will check newer versions. I will focus on
triggering the EPQ since that looks like a good lead.

Regards,
Anthonin Bonnefoy