Page History

...

Aside: I think making dag partitioning an explicit thing in airflow would be an overall good thing, beyond the whole uniqueness issue.  It clarifies what exactly is going on, i.e. why execution X does not run until the next partition – cus it would not be complete otherwise.  It also makes it possible for the user to say, every day rerun the last N partitions.  This is essentially a partition-driven workflow with a configurable lookback.

One thing I don't love about this is how to handle the case where the user 

4. Leave it sorta fuzzy and ambiguous

This is essentially the do nothing approach.  We more or less look the other way and don't worry about it.  Leave it how it is.  Backfill will look at the latest (by start_date) run for a given logical date to determine state. Similar elsewhere.  No protection against concurrent runs.  No well-defined view of data completeness.  

Backfill always only adds new rows to the dag run table.  It never "clears" an existing row to be rerun.

5. Distribute the logic elsewhere

...