Message-ID: <a5d42a2c-0c2e-9fb8-793f-0675d85669be@enterprisedb.com>
Date: Tue, 23 May 2023 22:57:31 +0200
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Subject: Re: memory leak in trigger handling (since PG12)
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To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
References: <222a3442-7f7d-246c-ed9b-a76209d19239@enterprisedb.com>
 <960113.1684859980@sss.pgh.pa.us>
From: Tomas Vondra <tomas.vondra@enterprisedb.com>
In-Reply-To: <960113.1684859980@sss.pgh.pa.us>
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On 5/23/23 18:39, Tom Lane wrote:
> Tomas Vondra <tomas.vondra@enterprisedb.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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