From: Tom Lane <tgl@sss.pgh.pa.us>
To: Scott Ribe <scott_ribe@elevated-dev.com>
cc: Pgsql-admin <pgsql-admin@lists.postgresql.org>
Subject: Re: update behavior
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References: <75F792AF-58DF-4559-A2E8-C89060D1E94E@elevated-dev.com>
Comments: In-reply-to Scott Ribe <scott_ribe@elevated-dev.com>
	message dated "Thu, 19 Jun 2025 11:23:58 -0600"
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Date: Thu, 19 Jun 2025 13:35:37 -0400
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Scott Ribe <scott_ribe@elevated-dev.com> writes:
> I believe that if I UPDATE a row with the same values that it already ha=
s, this still dirties pages, writes the row, generates a WAL entry. There =
is no shortcut in the processing that's "hey, there's not really a change =
here, we'll just leave storage alone".

> Is this correct?

It is.  We do offer a trigger you can add to suppress zero-change
updates [1], but that's not the default behavior.  We judged that
checking for that would add more cycles than it removes, for most
applications most of the time.

			regards, tom lane

[1] https://www.postgresql.org/docs/current/functions-trigger.html