Re: Unexpected behavior when combining `generated always` columns and update rules - Mailing list pgsql-general

On Thu, Apr 13, 2023 at 5:32 PM David G. Johnston
<david.g.johnston@gmail.com> wrote:
> ALSO rules behave like before triggers, not after triggers. The original command is appended to the end of the list
ofcommands, not the start. 


As Tom observed, the documentation states that in case of update
rules, the original query is executed at the end.

However, regardless of the order of the execution between new and
original query, as per the documentation the `new` table should
contain the new values regardless.

In fact, from my example above, one can see that the `y.x` is properly
updated with the new value, meanwhile the `y.d` is the previous one
(i.e. `old.d`).

So, based on these observations, I think that `generated always`
columns are actually computed on insertion, and thus they are not
reflected in `new` on rules.

Ciprian.