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Posted to commits@airflow.apache.org by "Arunodoy18 (via GitHub)" <gi...@apache.org> on 2025/12/26 07:11:00 UTC
[PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Arunodoy18 opened a new pull request, #59814:
URL: https://github.com/apache/airflow/pull/59814
This change addresses a critical performance issue where the Tasks tab in the DAG details view triggers N individual API calls for each task to fetch recent task instances, causing severe performance degradation and timeouts for DAGs with 200+ tasks.
Problem:
- Each TaskCard component independently called the API to fetch its task instances: /api/v2/dags/{dag_id}/dagRuns/~/taskInstances?task_id={task_id}
- For a DAG with 200 tasks, this resulted in 200+ sequential API calls
- Backend experienced SQLAlchemy timeouts due to excessive query load
- UI became unresponsive and unusable for large DAGs
Solution:
- Modified Tasks.tsx to batch-fetch all task instances for all tasks in a single API call using the existing batch endpoint: POST /api/v2/dags/~/dagRuns/~/taskInstances/list
- Task instances are grouped by task_id and passed as props to TaskCard
- Eliminated N+1 query pattern, reducing 200+ calls to just 1 call
- Maintained existing functionality including auto-refresh for pending tasks
Changes:
- Tasks.tsx: Added batch query using TaskInstanceService.getTaskInstancesBatch() with grouping logic to distribute instances to cards
- TaskCard.tsx: Modified to accept taskInstances as prop instead of fetching independently
Performance Impact:
- Reduces API calls from O(N) to O(1) where N is number of tasks
- For 200 tasks: 200 calls 1 call (99.5% reduction)
- Eliminates backend timeout issues
- Significantly improves UI responsiveness for large DAGs
Fixes: #59598
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Re: [PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Posted by "tirkarthi (via GitHub)" <gi...@apache.org>.
tirkarthi commented on code in PR #59814:
URL: https://github.com/apache/airflow/pull/59814#discussion_r2649441598
##########
airflow-core/src/airflow/ui/src/pages/Dag/Tasks/Tasks.tsx:
##########
@@ -57,6 +66,52 @@ export const Tasks = () => {
dagId,
});
+ // Extract task IDs for batch fetching task instances
+ const taskIds = data?.tasks.map((task) => task.task_id ?? "").filter((id) => id) ?? [];
+
+ // Batch fetch task instances for all tasks in one API call
+ const {
+ data: taskInstancesData,
+ error: taskInstancesError,
+ isFetching: isFetchingTaskInstances,
+ } = useQuery({
+ enabled: Boolean(dagId) && taskIds.length > 0,
+ queryFn: () =>
+ TaskInstanceService.getTaskInstancesBatch({
+ dagId: "~",
+ dagRunId: "~",
+ requestBody: {
+ dag_ids: [dagId],
+ order_by: "-run_after",
Review Comment:
`run_after` is not a valid sorting field on TaskInstance. On loading the tasks tab in dag details I can see below error.
```
400 Bad Request
Ordering with 'run_after' is disallowed or the attribute does not exist on the model
```
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Re: [PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Posted by "kaxil (via GitHub)" <gi...@apache.org>.
kaxil commented on code in PR #59814:
URL: https://github.com/apache/airflow/pull/59814#discussion_r2651039007
##########
airflow-core/src/airflow/ui/src/pages/Dag/Tasks/Tasks.tsx:
##########
@@ -57,6 +66,52 @@ export const Tasks = () => {
dagId,
});
+ // Extract task IDs for batch fetching task instances
+ const taskIds = data?.tasks.map((task) => task.task_id ?? "").filter((id) => id) ?? [];
+
+ // Batch fetch task instances for all tasks in one API call
+ const {
+ data: taskInstancesData,
+ error: taskInstancesError,
+ isFetching: isFetchingTaskInstances,
+ } = useQuery({
+ enabled: Boolean(dagId) && taskIds.length > 0,
+ queryFn: () =>
+ TaskInstanceService.getTaskInstancesBatch({
+ dagId: "~",
+ dagRunId: "~",
+ requestBody: {
+ dag_ids: [dagId],
+ order_by: "-run_after",
Review Comment:
**Please test your changes before creating PRs.** If you're using AI tools to help with development (which is fine!), you must review and test the generated code thoroughly. The volume of untested AI-generated PRs creates significant review burden for maintainers.
To test this properly:
1. Run the UI locally, check the contributing guide on how if unsure!
2. Navigate to a DAG with 200+ tasks
3. Open the Tasks tab and verify it loads without errors
4. Check the browser console and network tab for API calls
Would you like to revise this PR with a working implementation?
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Re: [PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Posted by "Shally-Katariya (via GitHub)" <gi...@apache.org>.
Shally-Katariya commented on code in PR #59814:
URL: https://github.com/apache/airflow/pull/59814#discussion_r2649454114
##########
airflow-core/src/airflow/ui/src/pages/Dag/Tasks/Tasks.tsx:
##########
@@ -57,6 +66,52 @@ export const Tasks = () => {
dagId,
});
+ // Extract task IDs for batch fetching task instances
+ const taskIds = data?.tasks.map((task) => task.task_id ?? "").filter((id) => id) ?? [];
+
+ // Batch fetch task instances for all tasks in one API call
+ const {
+ data: taskInstancesData,
+ error: taskInstancesError,
+ isFetching: isFetchingTaskInstances,
+ } = useQuery({
+ enabled: Boolean(dagId) && taskIds.length > 0,
+ queryFn: () =>
+ TaskInstanceService.getTaskInstancesBatch({
+ dagId: "~",
+ dagRunId: "~",
+ requestBody: {
+ dag_ids: [dagId],
+ order_by: "-run_after",
Review Comment:
Thanks for catching this .
You’re right — `run_after` is not a valid ordering field for TaskInstance, and using it results in a 400 error on the Tasks tab.
I verified this locally as well. We should switch to a supported ordering field (or remove explicit ordering if not required).
I’ll update the PR accordingly.
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Re: [PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Posted by "Shally-Katariya (via GitHub)" <gi...@apache.org>.
Shally-Katariya commented on PR #59814:
URL: https://github.com/apache/airflow/pull/59814#issuecomment-3693995645
I tested this locally using Breeze on the Tasks tab for `example_branch_labels`.
On the Tasks view, I no longer see per-task `taskInstances` API calls.
Instead, task data is loaded without N+1 requests, and task cards render correctly.
The refactor where Tasks.tsx batch-fetches task instances and passes them down to TaskCard works as expected.
This looks like a solid performance improvement 👍
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Re: [PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Posted by "Shally-Katariya (via GitHub)" <gi...@apache.org>.
Shally-Katariya commented on PR #59814:
URL: https://github.com/apache/airflow/pull/59814#issuecomment-3693926034
I went through the changes in Tasks.tsx and TaskCard.tsx.
Moving task instance fetching to the parent component and passing grouped data to TaskCard makes the data flow much cleaner and clearly avoids the N+1 API calls.
I'm continuing to read through the changes to understand edge cases for large DAGs. Happy to help with testing or follow-ups if needed.
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Re: [PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Posted by "potiuk (via GitHub)" <gi...@apache.org>.
potiuk commented on PR #59814:
URL: https://github.com/apache/airflow/pull/59814#issuecomment-3697540050
> Please test your changes before creating PRs. If you're using AI tools to help with development (which is fine!), you must review and test the generated code thoroughly. The volume of untested AI-generated PRs creates significant review burden for maintainers.
+10000
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Re: [PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Posted by "Arunodoy18 (via GitHub)" <gi...@apache.org>.
Arunodoy18 commented on PR #59814:
URL: https://github.com/apache/airflow/pull/59814#issuecomment-3692317163
I have done the changes regarding the issue posted in the issue tracker, If there is any issue regarding the approach , Do review and tell.
Thank you
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Re: [PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Posted by "Shally-Katariya (via GitHub)" <gi...@apache.org>.
Shally-Katariya commented on code in PR #59814:
URL: https://github.com/apache/airflow/pull/59814#discussion_r2649454114
##########
airflow-core/src/airflow/ui/src/pages/Dag/Tasks/Tasks.tsx:
##########
@@ -57,6 +66,52 @@ export const Tasks = () => {
dagId,
});
+ // Extract task IDs for batch fetching task instances
+ const taskIds = data?.tasks.map((task) => task.task_id ?? "").filter((id) => id) ?? [];
+
+ // Batch fetch task instances for all tasks in one API call
+ const {
+ data: taskInstancesData,
+ error: taskInstancesError,
+ isFetching: isFetchingTaskInstances,
+ } = useQuery({
+ enabled: Boolean(dagId) && taskIds.length > 0,
+ queryFn: () =>
+ TaskInstanceService.getTaskInstancesBatch({
+ dagId: "~",
+ dagRunId: "~",
+ requestBody: {
+ dag_ids: [dagId],
+ order_by: "-run_after",
Review Comment:
Thanks for catching this 👍
You’re right — `run_after` is not a valid ordering field for TaskInstance, and using it results in a 400 error on the Tasks tab.
I verified this locally as well. We should switch to a supported ordering field (or remove explicit ordering if not required).
I’ll update the PR accordingly.
--
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Re: [PR] Fix N+1 API calls issue in DAG Tasks tab [airflow]
Posted by "kaxil (via GitHub)" <gi...@apache.org>.
kaxil closed pull request #59814: Fix N+1 API calls issue in DAG Tasks tab
URL: https://github.com/apache/airflow/pull/59814
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Re: [PR] Fix N+1 query issue in DAG Tasks tab [airflow]
Posted by "Shally-Katariya (via GitHub)" <gi...@apache.org>.
Shally-Katariya commented on code in PR #59814:
URL: https://github.com/apache/airflow/pull/59814#discussion_r2649454114
##########
airflow-core/src/airflow/ui/src/pages/Dag/Tasks/Tasks.tsx:
##########
@@ -57,6 +66,52 @@ export const Tasks = () => {
dagId,
});
+ // Extract task IDs for batch fetching task instances
+ const taskIds = data?.tasks.map((task) => task.task_id ?? "").filter((id) => id) ?? [];
+
+ // Batch fetch task instances for all tasks in one API call
+ const {
+ data: taskInstancesData,
+ error: taskInstancesError,
+ isFetching: isFetchingTaskInstances,
+ } = useQuery({
+ enabled: Boolean(dagId) && taskIds.length > 0,
+ queryFn: () =>
+ TaskInstanceService.getTaskInstancesBatch({
+ dagId: "~",
+ dagRunId: "~",
+ requestBody: {
+ dag_ids: [dagId],
+ order_by: "-run_after",
Review Comment:
Thanks for catching this .
You’re right — `run_after` is not a valid ordering field for TaskInstance, and using it results in a 400 error on the Tasks tab.
I verified this locally as well. We should switch to a supported ordering field (or remove explicit ordering if not required).
--
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