Support DELETE -> INSERT as an option for applying a staging batch #212
Description
Some sources do not indicate that an UPDATE has occurred, but instead simply send an updated state of a record. This wouldn't be a problem for the merge, but consider this example:
Input 1:
Input 2, some time later:
Desired outcome here is to have only 1 row from the second input. Now, assuming we use location,product,segment as primary keys, first issue here would be selecting essentially a random record for insert. Moreover, in this case the real PK is location,product,segment,availableFrom which means we'll keep both records from Input 1.
Later on, since Input 2 is meant to replace data, we'll end up updating record 1 but keeping record two.
Fundamental issue with this type of source is, of course, the way it treats primary keys. Essentially updates are dumped on location,product,segment level, but real PK for the input/target is location,product,segment,availableFrom.