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From: Tomas Vondra <[email protected]>
To: Tom Lane <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: memory leak in trigger handling (since PG12)
Date: Tue, 23 May 2023 22:57:31 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>



On 5/23/23 18:39, Tom Lane wrote:
> Tomas Vondra <[email protected]> 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
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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