Subject: Re: doc correction
To: jasonwang.public@gmail.com, pgsql-docs@lists.postgresql.org
References: <157230251103.1057.6793271848303174613@wrigleys.postgresql.org>
From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Organization: 2ndQuadrant
Message-ID: <d3619b02-fb8f-e04f-d01d-9654526ccfe0@2ndquadrant.com>
Date: Tue, 29 Oct 2019 10:17:24 +0100
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On 2019-10-28 23:41, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
> 
> Page: https://www.postgresql.org/docs/12/ddl-generated-columns.html
> Description:
> 
> https://www.postgresql.org/docs/12/ddl-generated-columns.html
> 
> In the below
> "Consider the differences between a column with a default and a generated
> column. The column default is evaluated once when the row is first inserted
> if no other value was provided; a generated column is updated whenever the
> row changes and cannot be overridden. A column default may not refer to
> other columns of the table; a generation expression would normally do so. A
> column default can use volatile functions, for example random() or functions
> referring to the current time; this is not allowed for generated columns."
> 
> "a generation expression would normally do so" should be changed to "a
> generated column" for easier reading

The current wording seems more precise.  It's the expression that does 
the referencing, not the column itself.  There could be other things 
attached to a column to could reference other things or not.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services