* Before, we would get the min and max pk of the set we are to gather.
This changeset removes that.
* Before, we would, basically, know the size of the set we are to gather
and would query 100,000 of those job event records at a time. That logic
is now gone.
* Now, for unpartitioned job events we gather 4 hours at a time by
created time.
* Now, for partitioned job events we gather 4 hours at a time by
modified time.
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