bramhanandlingala opened a new pull request, #67426:
URL: https://github.com/apache/airflow/pull/67426
## Issue
When you configure Airflow with multiple executors and only some of them opt
in to `pre_assigns_external_executor_id` (like CeleryExecutor does), the
scheduler builds a SQL `CASE` expression to decide which task instances get a
UUID assigned:
```sql
CASE
WHEN task_instance.executor IN ('celery', 'celery.module.path') THEN
gen_random_uuid()
ELSE task_instance.external_executor_id
END
```
PostgreSQL takes one look at this and bails: "CASE types text and uuid
cannot be matched". The THEN branch returns a native UUID type (that's what
gen_random_uuid() produces in PostgreSQL), but the ELSE branch returns TEXT.
because external_executor_id was changed from VARCHAR to TEXT in migration
0102. Postgres won't implicitly coerce between the two.
MySQL and SQLite are fine, their UUID() / uuid4() functions already return
plain strings.
## The Fix
One line in the PostgreSQL compiler for random_db_uuid:
# before
return "gen_random_uuid()"
# after
return "gen_random_uuid()::text"
Casting to ::text makes the THEN branch the same type as the ELSE branch.
This also matches what random_db_uuid already declares as its SQLAlchemy type
(type = String()), so this was always the intended behaviour. the cast was just
missing.
## Test
Added
test_executable_task_instances_to_queued_mixed_executors_external_executor_id
which wires up two executors (one opt-in, one not), routes task instances to
each, and calls _executable_task_instances_to_queued. On PostgreSQL this
directly exercises the CASE path that was crashing. The test also asserts that
only the TI routed to the opt-in executor gets a UUID, and the other keeps None.
Are you willing to merge this PR?
Yes If it helps
Code of Conduct
I agree to follow this project's [Code of
Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
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