ColtenOuO opened a new pull request, #67304:
URL: https://github.com/apache/airflow/pull/67304
`BulkTaskInstanceService.handle_bulk_delete` re-queried the database once
per task instance inside the delete loop, even though
`_categorize_task_instances` had already loaded every matched task instance
into `task_instances_map`.
The "all map index" branch of the same method already batches its lookup
correctly — only the "specific `(task_id, map_index)`" branch had the N+1.
## Database round trips (N = task instances deleted)
Each redundant `SELECT` is one extra DB round trip. The fix reuses the
in-memory `task_instances_map`, so those N re-fetch round trips are removed:
| N (task instances) | Round trips before | Round trips after |
|--------------------|--------------------|-------------------|
| 5 | 15 | 10 |
| 10 | 25 | 15 |
| 20 | 45 | 25 |
Before: `5 + 2N` queries — N of them redundant re-fetches.
After: `5 + N` queries — exactly **N round trips eliminated** per bulk
delete.
## Fix
Capture the `task_instances_map` returned by `_categorize_task_instances`
(previously discarded with `_`) and look each task instance up in it instead of
issuing a fresh `SELECT` in the loop. Every key in `matched_task_keys` is a key
of that map, so the lookup is guaranteed to hit.
## Validation plan
1. Added `test_bulk_delete_does_not_requery_each_task_instance`: deletes two
differently-sized batches (5 and 15) and asserts each extra task instance
adds exactly one query — the removed re-query would roughly double the
delta.
2. Confirmed the test **fails on the pre-fix code** (query delta 20 instead
of 10, i.e. doubled) and **passes with the fix**, so it genuinely guards the
regression.
3. Ran the full `TestBulkTaskInstances` suite (27 tests) — all pass; bulk
delete / update / wildcard / authorization behaviour is unchanged.
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##### Was generative AI tooling used to co-author this PR?
- [X] Yes — Claude Code (Opus 4.7)
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