ddl: load cloud storage before picking add-index backfill

[D3Hunter]

What problem does this PR solve?

Issue Number: close #69731

Problem Summary:

For distributed fast-reorg ADD INDEX with tidb_cloud_storage_uri configured, initForReorgIndexes picked the backfill type before loadCloudStorageURI populated job.ReorgMeta.UseCloudStorage. As a result, the ingest path could run the local disk precheck even though global-sort cloud storage should bypass local disk usage checks.

What changed and how does it work?

Load the cloud-storage URI before selecting the add-index backfill type during reorg initialization. This keeps job.ReorgMeta.UseCloudStorage as the existing source of truth for pickBackfillType, so cloud-storage/global-sort jobs select ingest backfill without touching local disk precheck.

A regression case was added to TestPickBackfillType with a disk root that fails if local precheck is reached. The test verifies a distributed fast-reorg job with cloud storage configured sets UseCloudStorage and selects ReorgTypeIngest.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Test commands:

./tools/check/failpoint-go-test.sh pkg/ddl -run TestPickBackfillType -count=1
./tools/check/failpoint-go-test.sh pkg/ddl -run TestPickBackfillType -count=1 -tags=intest,deadlock,nextgen
make lint
git diff --check

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

Fix an issue that ADD INDEX with global sort could fail due to a local ingest disk precheck before loading cloud storage configuration.

Summary by CodeRabbit

• Bug Fixes
  • Improved index backfill behavior when cloud storage is configured, ensuring the cloud-backed ingest path is selected correctly.
  • Added coverage for cloud storage setups to skip unnecessary local disk prechecks, preventing avoidable test failures.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: e1fbacd9-5839-453d-9527-d4b7f718367f

📥 Commits

Reviewing files that changed from the base of the PR and between dbc8a91 and d6cbac6.

📒 Files selected for processing (1)

• pkg/ddl/backfilling_test.go

---

📝 Walkthrough

Walkthrough

Moves cloud storage metadata loading ahead of backfill type selection in initForReorgIndexes, and adds a test that configures cloud storage with a failing local disk precheck to verify ingest selection still proceeds.

Changes

Cloud storage precheck ordering fix

Layer / File(s)	Summary
Reorder loadCloudStorageURI before pickBackfillType pkg/ddl/index.go	loadCloudStorageURI(w, job) is now called before pickBackfillType(job) in initForReorgIndexes, and the earlier later call site is removed.
Test skip of local precheck under cloud storage pkg/ddl/backfilling_test.go	Adds a TestPickBackfillType subtest using testfailpoint to force the ingest environment check to fail, then verifies UseCloudStorage is set and ReorgTp becomes model.ReorgTypeIngest.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• pingcap/tidb#68558: Also changes how ReorgMeta.UseCloudStorage is used during DDL backfilling and reorg flow selection.
• pingcap/tidb#69096: Also adjusts UseCloudStorage-driven backfill behavior in related DDL paths.

Suggested reviewers: joechenrh, wjhuang2016

Poem

I hopped past tmp space, one soft little bound,
Cloud storage loaded before checks came around.
With a failpoint in tow, the rabbit says “yay,”
Ingest takes the path and keeps going today. 🐇

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main behavior change: loading cloud storage before selecting add-index backfill.
Description check	✅ Passed	The description includes the required issue number, change summary, tests, side effects, and release note, but the Problem Summary field is left blank.
Linked Issues check	✅ Passed	The code loads cloud storage earlier and adds a regression test that matches the linked issue's expected fix.
Out of Scope Changes check	✅ Passed	The changes stay focused on the reported ADD INDEX reorg ordering bug and its regression test.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.12.2)

level=error msg="Running error: context loading failed: failed to load packages: failed to load packages: failed to load with go/packages: context deadline exceeded"
level=error msg="Timeout exceeded: try increasing it by passing --timeout option"

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[D3Hunter]

/cherry-pick release-nextgen-202603

[ti-chi-bot]

@D3Hunter: once the present PR merges, I will cherry-pick it on top of release-nextgen-202603 in the new PR and assign it to you.

Details

In response to this:

/cherry-pick release-nextgen-202603

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.7447%. Comparing base (c22327f) to head (d6cbac6).
⚠️ Report is 13 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #69733        +/-   ##
================================================
- Coverage   76.3235%   75.7447%   -0.5789%     
================================================
  Files          2041       2079        +38     
  Lines        560482     585967     +25485     
================================================
+ Hits         427780     443839     +16059     
- Misses       131801     139299      +7498     
- Partials        901       2829      +1928     

Flag	Coverage Δ
integration	45.9602% <100.0000%> (+6.2550%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	60.4471% <ø> (ø)
parser	∅ <ø> (∅)
br	63.8036% <ø> (+1.0822%)	⬆️

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[ingress-bot]

🔍 Starting code review for this PR...

[ingress-bot]

This review was generated by AI and should be verified by a human reviewer.
Manual follow-up is recommended before merge.

Summary

• Total findings: 3
• Inline comments: 1
• Summary-only findings (no inline anchor): 2

Findings (highest risk first)

🟡 [Minor] (3)

1. Ordering dependency between loadCloudStorageURI and pickBackfillType is undocumented (pkg/ddl/index.go:1359, pkg/ddl/index.go:1822, pkg/ddl/index.go:1851)
2. New 8-method fake DiskRoot duplicates the existing PreCheckUsage failpoint hook (pkg/ddl/backfilling_test.go:134, pkg/ddl/ingest/disk_root.go:158)
3. New test double breaks the package's mock/fake naming convention (pkg/ddl/backfilling_test.go:134)

Unanchored findings

🟡 [Minor] (2)

1. New 8-method fake DiskRoot duplicates the existing PreCheckUsage failpoint hook
   • Request: Keep ingest.LitDiskRoot as the real diskRootImpl and enable the existing mockIngestCheckEnvFailed failpoint for the subtest instead of introducing a new fake type that must track the full DiskRoot interface.
2. New test double breaks the package's mock/fake naming convention
   • Request: Rename to something like mockDiskRootWithFailedPreCheck (or mockFailingPreCheckDiskRoot) to keep the test-double naming convention consistent across pkg/ddl.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: GMHDBJD, wjhuang2016

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Needs approval from an approver in each of these files:

• pkg/ddl/OWNERS [GMHDBJD,wjhuang2016]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-07-09 06:04:15.972843822 +0000 UTC m=+261642.008938888: ☑️ agreed by wjhuang2016.
• 2026-07-09 06:52:43.103359268 +0000 UTC m=+264549.139454325: ☑️ agreed by GMHDBJD.

[D3Hunter]

/retest

[D3Hunter]

/retest

[D3Hunter]

/retest

[ti-chi-bot]

@D3Hunter: new pull request created to branch release-nextgen-202603: #69740.

Details

In response to this:

/cherry-pick release-nextgen-202603

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.