Data engineering·Moving data out of the source
each run asks the source only for rows changed since the last run, and one row updated in the same second as the cutoff is now missing forever.
Incremental load
Also calleddelta load, incremental extract
Reading only what has changed since the previous run, tracked by a cursor of some kind. It is the standard way to make a big table affordable, and it introduces a whole class of quiet bug: rows changed exactly on the boundary, rows updated without their timestamp moving, and hard deletes, which by definition leave nothing to find. The failures are silent because a missing row does not error, it simply lowers a total.