Change approach to finding bad rows to LEFT OUTER JOIN.

[ashb]

Rather than sub-selects (two for count, or one for the CREATE TABLE).

For a large database (27m TaskInstances, 2m DagRuns) this takes the
time from 10minutes to around 3 minutes per table (we have 3) down to 3
minutes per table. (All times on Postgres.)

Tested:

• postges
• mysql
• mssql
• sqlite

Before:

CREATE TABLE _airflow_moved__2_3__dangling__rendered_task_instance_fields AS
SELECT
  rendered_task_instance_fields.dag_id AS dag_id,
  rendered_task_instance_fields.task_id AS task_id,
  rendered_task_instance_fields.execution_date AS execution_date,
  rendered_task_instance_fields.rendered_fields AS rendered_fields,
  rendered_task_instance_fields.k8s_pod_yaml AS k8s_pod_yaml +
FROM
  rendered_task_instance_fields
WHERE
  NOT (
    EXISTS (
      SELECT
        1
      FROM
        task_instance
        JOIN dag_run ON dag_run.dag_id = task_instance.dag_id
        AND dag_run.run_id = task_instance.run_id
      WHERE
        rendered_task_instance_fields.dag_id = task_instance.dag_id
        AND rendered_task_instance_fields.task_id = task_instance.task_id
        AND rendered_task_instance_fields.execution_date = dag_run.execution_date
    )
  )

After:

CREATE TABLE _airflow_moved__2_3__dangling__rendered_task_instance_fields AS
SELECT
  rendered_task_instance_fields.dag_id AS dag_id,
  rendered_task_instance_fields.task_id AS task_id,
  rendered_task_instance_fields.execution_date AS execution_date,
  rendered_task_instance_fields.rendered_fields AS rendered_fields,
  rendered_task_instance_fields.k8s_pod_yaml AS k8s_pod_yaml +
FROM
  rendered_task_instance_fields
  LEFT OUTER JOIN dag_run ON rendered_task_instance_fields.dag_id = dag_run.dag_id
  AND rendered_task_instance_fields.execution_date = dag_run.execution_date
  LEFT OUTER JOIN task_instance ON dag_run.dag_id = task_instance.dag_id
  AND dag_run.run_id = task_instance.run_id
  AND rendered_task_instance_fields.task_id = task_instance.task_id
WHERE
  task_instance.dag_id IS NULL
  OR dag_run.dag_id IS NULL
;

---

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[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.

[jedcunningham]

I've tested this on mssql, both 2.1.4 and 2.2.5.

[jedcunningham]

I've also tested this on mysql, both 2.1.4 and 2.2.5.