Create the valid prepared rows, reporting each row's outcome. Invalid rows are
never sent. Uses createMany when the sink offers it; otherwise creates with
a bounded pool so a large file does not fire thousands of simultaneous
requests. Partial success is honoured: a failing row does not abort the rest.
Create the valid prepared rows, reporting each row's outcome. Invalid rows are never sent. Uses
createManywhen the sink offers it; otherwise creates with a bounded pool so a large file does not fire thousands of simultaneous requests. Partial success is honoured: a failing row does not abort the rest.