During a rollback from Airflow 3 to Airflow 2, the task_instance_history_id_seq PostgreSQL sequence was not being recreated. This caused task_instance_history inserts to fail with NULL constraint violations since the id column had no DEFAULT value for auto-increment.

Root Cause

In the upgrade path (migration 0060), the id column is dropped:
batch_op.drop_column("id")When PostgreSQL drops a column with an associated sequence, the sequence is also dropped (due to ownership).

Testing

1. Run command breeze start-airflow --executor CeleryExecutor --backend postgres
2. Down try downgarding airflow db downgrade --to-revision e00344393f31 -y
3. Verify Seq is getting created after downgrade

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