Re: Detection of which attributes should get set in update trigger

On Friday, November 10, 2023, Thiemo Kellner <thiemo(at)gelassene-pferde(dot)biz>
wrote:

> Hi all
>
> I have a view, that is a join over 4 tables (the setup of the rule
> question). I want to update the central table over the view (by an
> instead-of trigger). How can I determine, whether an attribute should get
> set to NULL, "new.XYZ is null" or whether it should be left alone. Is there
> a leave-me-alone function determining, whether an attribute is in the set
> clause of an update statement. I am thinking along the line code in the
> trigger function like
>
> update TABLE
> set XYZ = case
> when leave-me-alone (new.XYZ) then old.XYZ
> else new.XYZ
> end;
>
> And what about the where condition... hm, guess I am a bit confused.
>

IIUC, The NEW record is complete, with every value as it should be in the
newly saved tuple. There is no leave-me-alone concept. You don’t get to
know if the column was specified or not in the update command.

David J.