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Re: Cascade Trigger Not Firing

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Judy Loomis <hoodie.judy@xxxxxxxxx> writes:
> I have a trigger that updates a target column when some other columns
> change.
> There is another trigger on the target column to update another table (the
> column can be changed in other ways besides the first trigger).
> If I update the target column directly the expected trigger fires.
> But if the 1st trigger changes the target column and it wasn't in the list
> of updated columns, the 2nd trigger doesn't fire.
> Is this expected behavior?

Per the manual (NOTES section of the CREATE TRIGGER man page):

    A column-specific trigger (one defined using the UPDATE OF column_name
    syntax) will fire when any of its columns are listed as targets in the
    UPDATE command's SET list. It is possible for a column's value to
    change even when the trigger is not fired, because changes made to the
    row's contents by BEFORE UPDATE triggers are not
    considered. Conversely, a command such as UPDATE ... SET x = x ...
    will fire a trigger on column x, even though the column's value
    did not change.

It's not really practical for trigger firings to depend on what other
triggers did or might do --- you'd soon end up with circularities.

			regards, tom lane





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