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From: Durgamahesh Manne <[email protected]>
To: Ron Johnson <[email protected]>
Cc: pgsql-general <[email protected]>
Subject: Re: Fillfactor effectiveness on existing table
Date: Wed, 11 Feb 2026 08:04:02 +0530
Message-ID: <CAJCZko+P6KM=xsgFs+oyR7AJghkXUc+_NbDuONdeQWJz+iQ8Mg@mail.gmail.com> (raw)
In-Reply-To: <CANzqJaBcssS-inkrW=cxqxd5_1-Re-0xY6totprgypSHC-mkmg@mail.gmail.com>
References: <CAJCZko+BFu4c4moqA5kMoJx3776xdYfEsxJQVNu_YYgrBmsCyQ@mail.gmail.com>
	<CAKFQuwYppwZRZQ128T+z638iMNGYcuLGHw42DD_AKSTnZu9QVQ@mail.gmail.com>
	<CANzqJaBcssS-inkrW=cxqxd5_1-Re-0xY6totprgypSHC-mkmg@mail.gmail.com>

On Tue, 10 Feb, 2026, 22:58 Ron Johnson, <[email protected]> wrote:

> On Tue, Feb 10, 2026 at 11:05 AM David G. Johnston <
> [email protected]> wrote:
>
>> On Tuesday, February 10, 2026, Durgamahesh Manne <
>> [email protected]> wrote:
>>
>>> Hi
>>>
>>> I added fillfactor with less than 100 to existing table then ran vacuum
>>> full to take effect
>>>
>>> How to ensure the applied fillfactor is working successfully
>>>
>>> A ratio of hot updates in catalog table should higher than value of
>>> n_dead_tup or n_tup_upd? Or what ?
>>>
>>>
>> While free space on the page is necessary for HOT, it is not sufficient.
>>
>> If you want to prove fillfactor isn’t buggy I’d suggest contriving a test
>> case instead inspecting complex real data.  A table with a single bigint
>> and say 50 fillfactor should be easily visible when inspecting the free
>> space of a page in the heap (not sure of the exact query for this though).
>> There is a page-inspect contrib extension that provides low-level details.
>>
>
> What about pgstattuple.free_space and free_percent?
>
> --
> Death to <Redacted>, and butter sauce.
> Don't boil me, I'm still alive.
> <Redacted> lobster!
>


Hi @Ron <[email protected]>
approx_free_space | 13227478672 approx_free_percent | 30.89065723142561

Free space can be considered as bloat for non toast table but not for both
toast and non toast I believe


Regards
Durga Mahesh

>

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