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From: Laurenz Albe <[email protected]>
To: Durgamahesh Manne <[email protected]>
To: pgsql-general <[email protected]>
Subject: Re: Fillfactor effectiveness on existing table
Date: Tue, 10 Feb 2026 19:31:08 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAJCZko+BFu4c4moqA5kMoJx3776xdYfEsxJQVNu_YYgrBmsCyQ@mail.gmail.com>
References: <CAJCZko+BFu4c4moqA5kMoJx3776xdYfEsxJQVNu_YYgrBmsCyQ@mail.gmail.com>

On Tue, 2026-02-10 at 21:25 +0530, Durgamahesh Manne wrote:
> 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 ?

Run

  SELECT n_tup_upd, n_tup_hot_upd
  FROM pg_stat_all_tables
  WHERE relname = 'your table';

Then wait for an hour and run the query again.

See how much "n_tup_upd" and "n_tup_hot_upd" increased in that hour.
If the increase is about the same for both, almost all of your UPDATEs
are HOT.

Yours,
Laurenz Albe

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