On Sat, 14 Sep 2019 10:00:18 -0500, Ron <ronljohnsonjr@gmail.com>
wrote:
>On 9/14/19 9:54 AM, Tom Lane wrote:
>[snip
>> The only mention of this feature in 38.1 "Overview of Trigger Behavior"
>> is
>>
>> UPDATE triggers*can* moreover be set to fire only if certain columns
>> are mentioned in the SET clause of the UPDATE statement.
>>
>> which seems to me to be plenty specific enough --- it is carefully
>> *not* saying that the trigger will fire if the column changes value.
>> The CREATE TRIGGER man page never says that, either.
>
>Given that the UPDATE "*can* ... be set to fire only if certain columns are
>mentioned in the SET clause of the UPDATE statement", it logically follows
>that the default behavior is something else (for example, if the field value
>changes for whatever reason.
But the default could be "any column mentioned", not necessarily any
value changed.
George