Re: How to know detailed information about HOT(Heap-Only Tuples)?

From: Luca Ferrari <fluca1978(at)infinito(dot)it>
To: 高健 <luckyjackgao(at)gmail(dot)com>
Cc: pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: How to know detailed information about HOT(Heap-Only Tuples)?
Date: 2013-08-22 06:30:39
Message-ID: CAKoxK+4=D2F-34dnqE7Hv1H+XcTSXK=X=NdjcmbwFywvq_3Rtg@mail.gmail.com
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On Thu, Aug 22, 2013 at 4:20 AM, 高健 <luckyjackgao(at)gmail(dot)com> wrote:

> according to a table, How many tuples are heap only tuples , and how many
> are not?
>

I believe there are not "hot tuples", a tuple is updated using HOT
depending on the indexes defined and the type of update itself.
Anyway, you can get an information of how many tuples have been
hot-touched via pg_stat_user_tables.n_tup_hot_upd

> And also , Is there any options which can influence HOT occurrance?

The storage setting (fillfactor) will change the hotness of your
tables, but of course this depends on the workload.

Luca

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