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Re: Fillfactor effectiveness on existing table
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* Re: Fillfactor effectiveness on existing table
@ 2026-02-10 17:28 Ron Johnson <[email protected]>
  2026-02-11 02:34 ` Re: Fillfactor effectiveness on existing table Durgamahesh Manne <[email protected]>
  0 siblings, 1 reply; 2+ messages in thread

From: Ron Johnson @ 2026-02-10 17:28 UTC (permalink / raw)
  To: pgsql-general <[email protected]>

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!


^ permalink  raw  reply  [nested|flat] 2+ messages in thread

* Re: Fillfactor effectiveness on existing table
  2026-02-10 17:28 Re: Fillfactor effectiveness on existing table Ron Johnson <[email protected]>
@ 2026-02-11 02:34 ` Durgamahesh Manne <[email protected]>
  0 siblings, 0 replies; 2+ messages in thread

From: Durgamahesh Manne @ 2026-02-11 02:34 UTC (permalink / raw)
  To: Ron Johnson <[email protected]>; +Cc: pgsql-general <[email protected]>

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

>


^ permalink  raw  reply  [nested|flat] 2+ messages in thread

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