Re: Bound memory usage during manual slot sync retries

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Xuneng Zhou <xunengzhou(at)gmail(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, "itsajin(at)gmail(dot)com" <itsajin(at)gmail(dot)com>, "Zhijie Hou (Fujitsu)" <houzj(dot)fnst(at)fujitsu(dot)com>
Subject: Re: Bound memory usage during manual slot sync retries
Date: 2026-05-26 23:39:34
Message-ID: CAA4eK1+mGigBhtZG3ZNZim0EDDcrEjauCTNp7S1166xesSRnFQ@mail.gmail.com
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On Tue, May 26, 2026 at 1:01 PM Xuneng Zhou <xunengzhou(at)gmail(dot)com> wrote:
>
>
>> On Mon, May 25, 2026 at 7:03 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>> >
>> > Okay, then let's go with a per-retry memory context approach.
>> >
>> > @@ -579,6 +579,8 @@ drop_local_obsolete_slots(List *remote_slot_list)
>> > local_slot->data.database));
>> > }
>> > }
>> > +
>> > + list_free(local_slots);
>> > }
>> >
>> > Why do we need this retail pfree if the caller is using memory context?
>> >
>>
>> I see that the latest patch in email [1] has already addressed this
>> point. So, I'll push the v2 version.
>>
>> [1] - https://www.postgresql.org/message-id/CABPTF7WB4Z62sPoZkhSygOCAo3OiTDLpMELxZDuwCb3HYgM_pQ%40mail.gmail.com
>
>
> Thanks. My original reasoning for adding the pfree here was to act as a safety guard in case other future callers might not manage the memory properly. But Zhijie pointed out that this double-free pattern is not favored in previous community discussions. I'll post the worst-case test and its results later.
>

Pushed.

--
With Regards,
Amit Kapila.

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