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Message-ID: <53dd03d4-5aab-405d-bff3-f3c5433edef7@garret.ru>
Date: Thu, 9 Jul 2026 13:08:43 +0300
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Subject: Re: BUG #19519: REPACK can fail due to missing chunk for toast value
To: Michael Paquier <michael@paquier.xyz>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>,
 Srinath Reddy Sadipiralla <srinath2133@gmail.com>,
 Matthias van de Meent <boekewurm+postgres@gmail.com>,
 Imran Zaheer <imran.zhir@gmail.com>, Alexander Lakhin <exclusion@gmail.com>,
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From: Konstantin Knizhnik <knizhnik@garret.ru>
In-Reply-To: <ak806l8j5A45y2LD@paquier.xyz>
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On 09/07/2026 8:43 AM, Michael Paquier wrote:
> On Thu, Jul 09, 2026 at 08:17:06AM +0300, Konstantin Knizhnik wrote:
>> Changing `table_relation_fetch_toast_slice` signature breaks compatibility
>> with some extensions, for example duckdb.
>> I wonder if we can change only  `bool (*relation_fetch_toast_slice)(...,
>> bool missing_ok)` callback signature, but preserve signature of
>> `table_relation_fetch_toast_slice`, adding one more function
>> `table_relation_try_fetch_toast_slice`:
> Thanks for the input.
>
> Adding more functions implies to change the size of TableAmRoutine,
> which may be bad.  For now I'd be tempted to just focus on how to fix
> the problem on HEAD in a way we are happy with.  We could sort out an
> optional back-branch version as a second step.
> --
> Michael

Sorry, I do not suggest to extend TableAmRoutine - it will contain 
single `relation_fetch_toast_slice` entry with new signature.

I suggest to add only new wrapper function 
`table_relation_try_fetch_toast_slice`, preserving original 
`table_relation_fetch_toast_slice`. It will preserve compatibility with 
extensions (there are not using TableAmRoutine directly) and do not 
extend TableAmRoutine.

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    <div class="moz-cite-prefix">On 09/07/2026 8:43 AM, Michael Paquier
      wrote:<br>
    </div>
    <blockquote type="cite" cite="mid:ak806l8j5A45y2LD@paquier.xyz">
      <pre wrap="" class="moz-quote-pre">On Thu, Jul 09, 2026 at 08:17:06AM +0300, Konstantin Knizhnik wrote:
</pre>
      <blockquote type="cite">
        <pre wrap="" class="moz-quote-pre">Changing `table_relation_fetch_toast_slice` signature breaks compatibility
with some extensions, for example duckdb.
I wonder if we can change only  `bool (*relation_fetch_toast_slice)(...,
bool missing_ok)` callback signature, but preserve signature of
`table_relation_fetch_toast_slice`, adding one more function
`table_relation_try_fetch_toast_slice`:
</pre>
      </blockquote>
      <pre wrap="" class="moz-quote-pre">
Thanks for the input.

Adding more functions implies to change the size of TableAmRoutine,
which may be bad.  For now I'd be tempted to just focus on how to fix
the problem on HEAD in a way we are happy with.  We could sort out an
optional back-branch version as a second step.
--
Michael</pre>
    </blockquote>
    <p>Sorry, I do not suggest to extend <span
      style="white-space: pre-wrap">TableAmRoutine</span> - it will
      contain single `<span style="white-space: pre-wrap">relation_fetch_toast_slice` entry with new signature.</span></p>
    <p>I suggest to add only new wrapper function <span
      style="white-space: pre-wrap">`table_relation_try_fetch_toast_slice`,
preserving original `</span><span style="white-space: pre-wrap">table_relation_fetch_toast_slice`.
It will preserve compatibility with extensions (there are not using </span><span
      style="white-space: pre-wrap">TableAmRoutine directly) and do not extend </span><span
      style="white-space: pre-wrap"></span><span
      style="white-space: pre-wrap">TableAmRoutine.</span></p>
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