Drop a downstream or upstream task dependency in Airflow

[gmyrianthous]

Assuming we have the two following Airflow tasks in a DAG,

from airflow.operators.dummy import DummyOperator

t1 = DummyOperator(task_id='dummy_1')
t2 = DummyOperator(task_id='dummy_2')

we can specify dependencies as:

# Option A
t1 >> t2

# Option B
t2.set_upstream(t1)

# Option C
t1.set_downstream(t2)

---

My question is whether there is any functionality that lets you remove downstream and/or upstream dependencies once they are defined.

I have a fairly big DAG where most of the tasks (and their dependencies) are generated dynamically. Once the tasks are created, I would like to re-arrange some of the dependencies and/or introduce some new tasks.

For example, assuming that the functionality implements the following logic

from airflow.operators.dummy import DummyOperator

t1 = DummyOperator(task_id='dummy_1')
t2 = DummyOperator(task_id='dummy_2')

t1 >> t2

I would like to then be able to add a new task, add it in between the two tasks, and then remove the old dependency between t1 and t2. Is this possible?

t3 = DummyOperator(task_id='dummy_3')
t1 >> t3
t3 >> t2 
# Somehow remove t1 >> t2

[hussein-awala]

I am not sure if this works, but you can try it:

t1.downstream_task_ids.pop("dummy_2")
t2.upstream_task_ids.pop("dummy_1")

[gmyrianthous]

This does work (or t1.downstream_task_ids.remove('dummy_2')).

By any chance, do you know if this imposes any issues (i.e. when removing tasks from downstream_task_ids and upstream_task_ids property) ?