Re: memory leak in trigger handling (since PG12)

On 5/23/23 18:39, Tom Lane wrote:
> Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> writes:
>> it seems there's a fairly annoying memory leak in trigger code,
>> introduced by
>> ...
>> Attached is a patch, restoring the pre-12 behavior for me.
>
>> While looking for other places allocating stuff in ExecutorState (for
>> the UPDATE case) and leaving it there, I found two more cases:
>
>> 1) copy_plpgsql_datums
>
>> 2) make_expanded_record_from_tupdesc
>> make_expanded_record_from_exprecord
>
>> All of this is calls from plpgsql_exec_trigger.
>
> Not sure about the expanded-record case, but both of your other two
> fixes feel like poor substitutes for pushing the memory into a
> shorter-lived context. In particular I'm quite surprised that
> plpgsql isn't already allocating that workspace in the "procedure"
> memory context.
>

I don't disagree, but which memory context should this use and
when/where should we switch to it?

I haven't seen any obvious memory context candidate in the code calling
ExecGetAllUpdatedCols, so I guess we'd have to pass it from above. Is
that a good idea for backbranches ...

regards

--
Tomas Vondra
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