Re: Table bloat threshold limit to trigger repack - Mailing list pgsql-general

From Peter J. Holzer
Subject Re: Table bloat threshold limit to trigger repack
Date
Msg-id ncmz2o6ia4dmd7up7uyfjerm5jdldkgbbtmdn5pp2couhkqj74@dcxzipl44bxi
Whole thread
In response to Re: Table bloat threshold limit to trigger repack  (Durgamahesh Manne <maheshpostgres9@gmail.com>)
List pgsql-general
On 2026-02-08 15:14:37 +0530, Durgamahesh Manne wrote:
> On Sun, 8 Feb, 2026, 13:15 Ron Johnson, <ronljohnsonjr@gmail.com> wrote:
>     On Sun, Feb 8, 2026 at 12:43 AM Durgamahesh Manne <
>     maheshpostgres9@gmail.com> wrote:
>         On Sun, 8 Feb, 2026, 10:59 Ron Johnson, <ronljohnsonjr@gmail.com>
>         wrote:
>             On Sat, Feb 7, 2026 at 11:19 PM Durgamahesh Manne <
>             maheshpostgres9@gmail.com> wrote:
>                 How much table bloat is acceptable before it affects
>                 performance in PostgreSQL? 
>
>             How big is the table? (For small tables, it doesn't matter.) How
>             active is it?  How frequently are records updated?
>
>         Table size 100gb
>         I use pgstattuple_approx to get Table bloat is about 16gb as of now
>         since after repack is done on 27th of January 
>         Fillfactor already in place
>         It's very critical application with updates on non partitioned table 
>
>
>     What did you set the fillfactor to?
>     Have you minimized the number of indexes?  (That lets HOT work better.)
>     How long does it take to VACUUM the table?
>
> Fillfactor 80

With a fillfactor of 80 you should expect at least 20% of unused space,
or a "bloat" of (100 / 80) - 100 = 25 %.

Your 16 GB seem to be less than that which is a bit unexpected, but
might happen if you have an update-heavy workload. If you have 16 GB
more bloat than expected (i.e. you have 67 GB of data and therefore
expected a table size of 67 * 100 / 80 = 84 GB, but have 100 GB
instead), that may be worth investigating but isn't terribly concerning
if you have many inserts.

        hjp

--
   _  | Peter J. Holzer    | Story must make more sense than reality.
|_|_) |                    |
| |   | hjp@hjp.at         |    -- Charles Stross, "Creative writing
__/   | http://www.hjp.at/ |       challenge!"

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