Re: Clarification of triggers with 'OF column_name' in 'Overview of Trigger Behavior'

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От David G. Johnston
Тема Re: Clarification of triggers with 'OF column_name' in 'Overview of Trigger Behavior'
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Msg-id CAKFQuwZg7rh9UsyLEn7+=fc-fvT2f4MDtbFehvCvrGte+YUTpQ@mail.gmail.com
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Ответ на Clarification of triggers with 'OF column_name' in 'Overview of Trigger Behavior'  (PG Doc comments form <noreply@postgresql.org>)
Ответы Re: Clarification of triggers with 'OF column_name' in 'Overview of Trigger Behavior'  ("David G. Johnston" <david.g.johnston@gmail.com>)
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On Mon, May 2, 2022 at 6:33 PM Josh Silver <josh.ag@paladin.insure> wrote:

and the  'Overview of Trigger Behavior pages says of before triggers
In row-level triggers the WHEN condition can examine the old and/or new values of columns of the row. (Statement-level triggers can also have WHEN conditions, although the feature is not so useful for them.) In a BEFORE trigger, the WHEN condition is evaluated just before the function is or would be executed, so using WHEN is not materially different from testing the same condition at the beginning of the trigger function.
 
but does not even mention column specific triggers by name.


The previous paragraph reads in part:

"If more than one trigger is defined for the same event on the same relation, the triggers will be fired in alphabetical order by trigger name."

I'll say that we don't provide a granular definition of what an "event" is here - namely the "INSERT/UPDATE/DELETE/SELECT + any column limitation".

So, it is covered if you understand the column aspect is rolled into "trigger event".

David J.

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