Re: repack with verbose output: not showing the number of removable row versions when using USING INDEX or CONCURRENTLY option

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Re: repack with verbose output: not showing the number of removable row versions when using USING INDEX or CONCURRENTLY option

От:
Jochen Bandhauer <jb@jbitc.de>
Дата:
On 26.08.2026 14:56, Jochen Bandhauer wrote:
> On 26.08.2026 02:44, Fujii Masao wrote:
>> On Wed, Aug 26, 2026 at 6:00 AM Jochen Bandhauer  wrote:
>>> Am 25. August 2026 21:57:44 MESZ schrieb Nathan Bossart 
>>> :
>>>> Does this one deserve a mention on the open items wiki [0]?
>>>>
>>>> [0] https://wiki.postgresql.org/wiki/PostgreSQL_19_Open_Items
>>>>
>>> I think yes. It's not critical to the functionality, but the verbose 
>>> output is not correct.
>> I agree that this should be fixed, but I wonder whether this is entirely
>> new in v19.
>>
>> AFAICS, the same kind of misleading "removable" count can also occur 
>> with
>> CLUSTER USING INDEX in v18 and older releases, since the count depends
>> on the scan path. The CONCURRENTLY case is new, but the USING INDEX
>> case does not seem to be.
>>
>> So I'm not sure this should be considered a v19 blocker. Perhaps
>> documenting this limitation for now would be sufficient?
>>
>> Regards,
>>
> I have taken a closer look at this today and I found that the 
> "removable" count was probably influenced by page pruning in my 
> original bug report. This can also be seen with the cluster command in 
> v18. I would propose to add these lines to the Notes section of the 
> cluster and repack command documentation:
>
> The number of removable row versions shown in the verbose output 
> should not be considered a definitive measure of all dead tuples in 
> the table. It reflects the number of dead tuples encountered by the 
> specific scanning method (e.g., an index scan) that was used to 
> rebuild the table. In some cases, dead tuples may be physically 
> removed from the heap (pruned) before they are even encountered, 
> further influencing this count.
>
> What do you think?
>
> Jochen
>
I created two patches for the doc update for REL_18_STABLE and master.

Regards
Jochen

-- 
Mit freundlichen Grüßen

Jochen Bandhauer
+49 (0)176 29390012
www.jbitc.de

Re: repack with verbose output: not showing the number of removable row versions when using USING INDEX or CONCURRENTLY option

От:
Nathan Bossart <nathandbossart@gmail.com>
Дата:
Does this one deserve a mention on the open items wiki [0]?

[0] https://wiki.postgresql.org/wiki/PostgreSQL_19_Open_Items

-- 
nathan
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