The update keys are used to identify already existing rows which should be updated.
We make use of a bloom filter to avoid hitting the DB for every row -
the bloom filter gives us a definite answer for missing rows, and a 99% certainity for existing rows.
The update keys are used to identify already existing rows which should be updated. We make use of a bloom filter to avoid hitting the DB for every row - the bloom filter gives us a definite answer for missing rows, and a 99% certainity for existing rows.