Sync v3-0-stable with 3.0.5rc2 changes
#54520
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Fixes critical blocking issues when downgrading Airflow from 3.x to 2.x across PostgreSQL, MySQL, and SQLite databases. These issues were discovered after [PR apache#54399](apache#54399) unblocked the downgrade process. **Error:** ``` sqlalchemy.exc.IntegrityError: (psycopg2.errors.NotNullViolation) column "try_number" of relation "task_reschedule" contains null values ``` **Root Cause:** Migration [`0068_3_0_0_ti_table_id_unique_per_try.py:L99`](https://github.com/apache/airflow/blob/main/airflow-core/src/airflow/migrations/versions/0068_3_0_0_ti_table_id_unique_per_try.py#L99) uses `default="1"` instead of `server_default="1"`, causing existing NULL values to remain NULL when the column is made NOT NULL. **Solution:** Replace `default="1"` with `server_default="1"` to ensure database-level default value assignment. **Error:** ``` sqlalchemy.exc.IntegrityError: (psycopg2.errors.NotNullViolation) column "task_instance_id" of relation "task_instance_history" contains null values ``` **Root Cause:** The `task_instance_id` column is made NOT NULL during downgrade but contains NULL values, even though this column gets dropped entirely in the same migration. **Solution:** Make `task_instance_id` column nullable since it's immediately dropped and not needed in 2.x schema. **Error:** ``` sqlalchemy.exc.OperationalError: (MySQLdb.OperationalError) (1138, 'Invalid use of NULL value') ``` **Root Cause:** MySQL query attempts to JOIN on NULL `id` values in `task_instance_history`: ```sql UPDATE task_instance_history tih JOIN ( SELECT id, ROW_NUMBER() OVER (ORDER BY id) AS row_num FROM task_instance_history ) AS temp ON tih.id = temp.id SET tih.id = temp.row_num; ``` The `id` column was just re-added as nullable with all NULL values, making the JOIN fail. **Solution:** Replace with MySQL variable-based sequential numbering: ```sql SET @row_number = 0; UPDATE task_instance_history SET id = (@row_number := @row_number + 1) ORDER BY try_id; ``` **Error:** ``` sqlalchemy.exc.IntegrityError: (sqlite3.IntegrityError) FOREIGN KEY constraint failed ``` **Root Cause:** SQLite's strict foreign key checking prevents dropping the `dag` table during `batch_alter_table` operations when other tables reference it. **Solution:** Add SQLite-specific handling to temporarily disable foreign key constraints: ```python if dialect_name == "sqlite": conn.execute(text("PRAGMA foreign_keys=OFF")) try: # batch operations finally: conn.execute(text("PRAGMA foreign_keys=ON")) ``` Verified successful downgrade from Airflow 3.0.5rc1 to 2.11 on: - [x] PostgreSQL - [x] MySQL - [x] SQLite (cherry picked from commit bc18493)
boring-cyborg
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area:db-migrations
jedcunningham
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Aug 14, 2025
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Changes from rc1: #54508
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