Zitat von Daniel Verite <daniel@xxxxxxxxxxxxxxxx>:
Thiemo Kellner, NHC Barhufpflege wrote:
> Why you don't create query like
>
> EXECUTE 'SELECT xxx FROM TAB WHERE A = $1.x AND B = $1.y' USING NEW;
I shall try. This would be the direct way, but I doubt the placeholder
$1 can be a record.
It could be written without refering to any individual column:
IF EXISTS (select 1 from tablename
where tablename.* is not distinct from NEW)
THEN
-- do something
END IF;
Wow, I shall see if I can apply this pattern to more.
But since the select cannot see not-yet-committed changes from other
sessions, such a trigger cannot reliably detect duplicates, unless
you make sure that there are no concurrent writes to the table.
This is not trigger specific but always a problem of concurrency. If
you let two processes do SCD2 on the same table at the same time on
the same business keys, you will get a messed-up table.
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