kaxil opened a new pull request #13892:
URL: https://github.com/apache/airflow/pull/13892
While developing locally to fix a Scheduler bug, I had to reset DB number of
times and this particular
migration caused problems (failed with following error):
```
INFO [alembic.runtime.migration] Running upgrade cf5dc11e79ad ->
bbf4a7ad0465, Remove id column from xcom
INFO [alembic.runtime.migration] Running upgrade bbf4a7ad0465 ->
b25a55525161, Increase length of pool name
INFO [alembic.runtime.migration] Running upgrade b25a55525161 ->
3c20cacc0044, Add DagRun run_type
INFO [alembic.runtime.migration] Running upgrade 3c20cacc0044 ->
8f966b9c467a, Set conn_type as non-nullable
INFO [alembic.runtime.migration] Running upgrade 8f966b9c467a ->
8d48763f6d53, add unique constraint to conn_id
INFO [alembic.runtime.migration] Running upgrade 8d48763f6d53 ->
e38be357a868, Add sensor_instance table
Traceback (most recent call last):
File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py",
line 1277, in _execute_context
cursor, statement, parameters, context
File
"/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line
609, in do_execute
cursor.execute(statement, parameters)
psycopg2.errors.DuplicateTable: relation "sensor_instance" already exists
```
Making it idempotent helps us to run it multiple times
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