问题
Can any one please explain Why joiner is not used after Sequence generator or Update statergy?
回答1:
It's because joiner may render useless the logic achieved until those two transformation.
Joiner after sequence generator - Purpose of a sequence generator is to generate a new or missing key value. Depending on the join type, you may drop this key value.
Joiner after update strategy - Purpose of update strategy is to determine how a record needs to be processed into the database - insert/update/delete. This decision generally gets made when all the data has been pulled in and every logic/transformation has been applied. Depending on the join type you might miss essential changes to your database.
来源：https://stackoverflow.com/questions/30197877/why-joiner-is-not-used-after-sequence-generator-or-update-statergy