Cascade update of taskinstance to TaskMap table

[ephraimbuddy]

Updating a taskinstance's map_index etc should cascade to the task_map table
else we would get foreign key violation error when updating a task instance from unmapped
to mapped.

closes: #31431

[uranusjr]

Would this be performant if the tables contain a lot of rows? I seem to recall creating a new index has performance issues.

[ephraimbuddy]

Would this be performant if the tables contain a lot of rows? I seem to recall creating a new index has performance issues.

Do you mean a performance issue when upgrading? Like taking a lot of time to run the upgrade? I don't think there would be a performance issue but it's worth testing

[uranusjr]

Yes when upgrading.

[jedcunningham]

(assuming no catastrophic performance issues are found)

[ephraimbuddy]

I have tested the upgrade and downgrade with 17million rows in taskinstance and dagrun tables, 15million rows in task_map table.
The test was done with airflow 2.6.1.
Upgrade: airflow db upgrade 1.26s user 0.20s system 10% cpu 14.438 total
Downgrade: airflow db downgrade --to-version 2.6.1 0.78s user 0.17s system 5% cpu 15.969 total

So a total of 1.26s for upgrade and 0.78s for downgrade

Below is the full log of the test: