Add missing indexes on dag_version_id columns for db cleanup performance

[GaneshPatil7517]

What does this PR do?

Adds database indexes on task_instance.dag_version_id and dag_run.created_dag_version_id to fix the slow performance of airflow db clean -t dag_version command.

Why is this needed?

When running airflow db clean -t dag_version --batch-size 1000, the cleanup process was taking ~6 minutes per batch on tables with 300K+ rows. The root cause was missing indexes on the foreign key columns that reference dag_version.id.

The cleanup code in db_cleanup.py defines dag_version with dependent_tables=["task_instance", "dag_run"], meaning every delete operation needs to check both tables for FK violations. Without indexes, PostgreSQL performs full table scans.

What changed?

1. New migration (0098_3_2_0_add_dag_version_id_indexes_for_db_cleanup.py):

   • Adds idx_task_instance_dag_version_id on task_instance(dag_version_id)
   • Adds idx_dag_run_created_dag_version_id on dag_run(created_dag_version_id)

2. Updated ORM models: Added indexes to __table_args__ for schema consistency

Performance Impact

Scenario	Before	After
db clean -t dag_version (300K rows, batch=1000)	~6 min/batch	< 2 min total

Fixes #60145

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[Copilot]

Pull request overview

This pull request addresses a performance issue with the airflow db clean -t dag_version command by adding database indexes on foreign key columns that reference dag_version.id. Without these indexes, the cleanup process was performing full table scans resulting in ~6 minutes per batch on tables with 300K+ rows.

Changes:

• Added migration 0099 to create indexes on task_instance.dag_version_id and dag_run.created_dag_version_id
• Updated ORM models (TaskInstance and DagRun) to include the new indexes in their __table_args__
• Updated the database revision head mapping to point to the new migration

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
airflow-core/src/airflow/utils/db.py	Updated the 3.2.0 revision head to point to the new migration
airflow-core/src/airflow/models/taskinstance.py	Added index on dag_version_id column to table_args
airflow-core/src/airflow/models/dagrun.py	Added index on created_dag_version_id column to table_args
airflow-core/src/airflow/migrations/versions/0099_3_2_0_add_dag_version_id_indexes_for_db_cleanup.py	New migration that creates the indexes with proper upgrade/downgrade logic
airflow-core/docs/migrations-ref.rst	Updated migration reference documentation to include the new migration as head

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