From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: Ilya Kosmodemiansky <ik@dataegret.com>,
        "Wetmore,
    Matthew (CTR)" <Matthew.Wetmore@express-scripts.com>,
        pgsql-admin@lists.postgresql.org
Subject: Re: GENERATE AS
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Comments: In-reply-to "David G. Johnston" <david.g.johnston@gmail.com>
	message dated "Thu, 22 Jun 2023 13:25:34 -0700"
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Date: Thu, 22 Jun 2023 17:15:05 -0400
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"David G. Johnston" <david.g.johnston@gmail.com> writes:
> The problem here is not timezone related - it is more fundamental in that
> the stored data does not change but the expression, as time progresses, is
> going to give different values and thus make what is stored incorrect.

Right --- current_timestamp in a generation expression makes no sense.
(There's also an issue about whether the surrounding calculation
is timezone-dependent, but that could be fixed up.  Depending on
current time cannot be.)

You could create a view in which this value is an extra computed column,
but you can't do it as a stored generated column.

			regards, tom lane