Re: vacuum full, why multiple times ?

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Richard Huxton wrote:
> Gaetano Mendola wrote:
>
>>
>> # vacuum full verbose url;
>> INFO: vacuuming "public.url"
>> INFO: "url": found 74 removable, 21266 nonremovable row versions in
>> 8550 pages
>> DETAIL: 2 dead row versions cannot be removed yet.
>> [SNIP]
>> INFO: "url": moved 11 row versions, truncated 8550 to 8504 pages
>>
>>
>> and in the next run:
>>
>>
>> # vacuum full verbose url;
>> INFO: vacuuming "public.url"
>> INFO: "url": found 13 removable, 21264 nonremovable row versions in
>> 8504 pages
>> DETAIL: 0 dead row versions cannot be removed yet.
>> [SNIP]
>> INFO: "url": moved 5666 row versions, truncated 8504 to 621 pages
>
>
> If page number 8549 was the one being held, I don't think vacuum can
> truncate the file. The empty space can be re-used, but the rows can't be
> moved to a lower page while a transaction is using them.

It's clear now.

Regards
Gaetano Mendola
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