perf(worker): Optimize flake processing by bulk updating testruns

[sentry]

Fixes WORKER-X12. The issue was that: process_flakes_for_commit iterates uploads, calling get_testruns per upload, causing N+1 database queries.

• Refactored get_testruns into get_testruns_for_uploads to fetch testruns for multiple uploads simultaneously.
• Modified get_testruns_for_uploads to return a dictionary mapping upload IDs to their respective testruns.
• Updated process_single_upload to accept testruns as an argument, removing individual database fetches.
• Centralized Testrun bulk updates in process_flakes_for_commit to perform a single update for all processed testruns, reducing database operations.
• Improved overall database efficiency by reducing the number of queries and bulk update calls during flake processing.

This fix was generated by Seer in Sentry, triggered automatically. 👁️ Run ID: 13507733

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Note

Medium Risk
Moderate risk: changes query/update behavior in flake detection by batching Testrun fetches and centralizing bulk_update, which could affect which rows are updated if upload IDs/filters are incorrect.

Overview
Improves process_flakes_for_commit performance by replacing per-upload get_testruns queries with a single get_testruns_for_uploads(upload_ids) query that groups recent Testruns by upload.

process_single_upload now consumes pre-fetched testruns, and outcome changes are persisted via one centralized Testrun.objects.bulk_update(...) after all uploads are processed (instead of per-upload updates).

^{Reviewed by Cursor Bugbot for commit 4bb87c4. Bugbot is set up for automated code reviews on this repo. Configure here.}

[sentry]

Bug: An exception during the processing loop in process_flakes_for_commit will cause all pending testrun outcome updates for the commit to be lost, as the final bulk_update is no longer atomic per-upload.
_{Severity: MEDIUM}

Suggested Fix

Wrap the processing for each upload within the main loop of process_flakes_for_commit in a with transaction.atomic(): block. This will ensure that database operations for each upload are treated as a single atomic unit, preventing partial updates and data inconsistency if an error occurs mid-process.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: apps/worker/services/test_analytics/ta_process_flakes.py#L143

Potential issue: The function `process_flakes_for_commit` was refactored to perform a
single `bulk_update` of testrun outcomes after processing all uploads for a commit.
However, the processing loop still contains individual database writes, such as
`flake.save()` within `handle_pass`. If a database exception occurs during one of these
individual writes, the function will exit prematurely. As a result, the final
`bulk_update` is never executed, causing all accumulated testrun outcome updates for
that commit to be lost. This can lead to data inconsistency, where a flake's state is
updated but the corresponding testrun outcome is not.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

[sentry]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.25%. Comparing base (0ad8a0c) to head (4bb87c4).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #853   +/-   ##
=======================================
  Coverage   92.25%   92.25%           
=======================================
  Files        1307     1307           
  Lines       48017    48025    +8     
  Branches     1636     1636           
=======================================
+ Hits        44299    44307    +8     
  Misses       3407     3407           
  Partials      311      311           

Flag	Coverage Δ
workerintegration	58.52% <13.33%> (-0.03%)	⬇️
workerunit	90.39% <100.00%> (+<0.01%)	⬆️

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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