ddl: load cloud storage before picking add-index backfill (#69733)

[ti-chi-bot]

This is an automated cherry-pick of #69733

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
  • Backfill operations now more reliably choose the correct processing mode when cloud storage is configured.
  • Improved handling of cloud-storage-backed reorganization so the system can select ingest-based processing as expected in supported scenarios.

[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: ce39ead6-418c-4d7e-9334-91cb5446502f

📥 Commits

Reviewing files that changed from the base of the PR and between 1f6df34 and 64bb104.

📒 Files selected for processing (2)

• pkg/ddl/backfilling_test.go
• pkg/ddl/index.go

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📝 Walkthrough

Walkthrough

initForReorgIndexes in pkg/ddl/index.go now calls loadCloudStorageURI before pickBackfillType, removing the later duplicate call. A test file adds a subtest to TestPickBackfillType that verifies UseCloudStorage and ReorgTp are correctly set when a cloud storage URI is configured alongside an ingest-check failpoint.

Changes

Cloud Storage Load Ordering Fix

Layer / File(s)	Summary
Reorder loadCloudStorageURI before pickBackfillType pkg/ddl/index.go	loadCloudStorageURI(w, job) is now called immediately after the idxInfos guard, before pickBackfillType(job), and the later duplicate call before the merge-process branch is removed.
Test for cloud storage detection with ingest failpoint pkg/ddl/backfilling_test.go	TestPickBackfillType gains a subtest that enables an ingest-check failpoint, sets vardef.CloudStorageURI, calls initForReorgIndexes, and asserts ReorgMeta.UseCloudStorage is true and ReorgTp is model.ReorgTypeIngest.

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

Possibly related PRs

• pingcap/tidb#68558: Both PRs deal with job.ReorgMeta.UseCloudStorage propagation affecting backfill/streaming decisions.
• pingcap/tidb#69096: Both PRs modify how UseCloudStorage is set and consumed by backfilling/reorg logic, including related failpoint testing.

Suggested labels: ok-to-test

Suggested reviewers: D3Hunter, joechenrh, GMHDBJD

Poem

A hop, a skip, a storage URI first,
Before the disk check quenches its thirst,
Now cloud paths load right in place,
No more failing at the ingest race,
This bunny thumps approval with delight! 🐇☁️

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states the main change: loading cloud storage before choosing add-index backfill.
Description check	✅ Passed	The description follows the template with issue number, problem summary, changes, tests, side effects, and release note.
Linked Issues check	✅ Passed	The changes match #69731 by loading cloud storage earlier so pickBackfillType can select ingest without local disk precheck.
Out of Scope Changes check	✅ Passed	The diff is limited to the intended index backfill ordering fix and a regression test, with no obvious unrelated changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ 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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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (release-nextgen-202603@1f6df34). Learn more about missing BASE report.

Additional details and impacted files

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Flag	Coverage Δ
unit	76.1428% <100.0000%> (?)

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Components	Coverage Δ
dumpling	61.5065% <0.0000%> (?)
parser	∅ <0.0000%> (?)
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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: D3Hunter, joechenrh

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Details

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• pkg/ddl/OWNERS [D3Hunter]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-07-09 14:28:40.6195639 +0000 UTC m=+291906.655658966: ☑️ agreed by D3Hunter.
• 2026-07-13 08:58:47.233154247 +0000 UTC m=+617713.269249293: ☑️ agreed by joechenrh.