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From: Ron Johnson <[email protected]>
To: pgsql-general <[email protected]>
Subject: Re: Fillfactor effectiveness on existing table
Date: Tue, 10 Feb 2026 22:02:36 -0500
Message-ID: <CANzqJaD_DifAmHS4B2JQH5ZLZ07J5nkLoNtLp9_jZD7Gk4zBXA@mail.gmail.com> (raw)
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On Tue, Feb 10, 2026 at 9:34 PM Durgamahesh Manne <[email protected]>
wrote:

>
>
> 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?
>>
> 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
>

1) Did you vacuum?
2) What's the fillfactor?

-- 
Death to <Redacted>, and butter sauce.
Don't boil me, I'm still alive.
<Redacted> lobster!

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