fix: HGraph dirty-vector search dereferences an empty result heap

[vsag-bot]

Summary

Fixed search- and construction-time empty candidate handling. The previously reproducible ASan overflow and dirty-vector result regression now pass under ASan/UBSan and TSAN.

Root Cause

Non-finite vectors can leave route-search and graph-construction candidate heaps empty. HGraph dereferenced those heaps, pruning accessed an empty neighbor vector, and disconnected dirty nodes could replace valid graph entry points.

Changes

• Guarded empty route results in KNN, range, request, and construction descent paths.
• Made mutual connection safely represent an empty candidate set.
• Prevented disconnected nodes from replacing HGraph and Pyramid entry points.
• Restored all newly created HGraph route levels after an unconnectable insertion.
• Added deterministic dirty-vector addition/search and empty-pruning regressions.

Validation

• clang-format-15 --dry-run --Werror <changed C++ files> && git diff --check: passed - Formatting and whitespace checks passed.
• cmake --build build-tsan-ai-clean --parallel 4: passed - Complete TSAN build passed; final affected sources and targets rebuilt successfully.
• TSAN focused unit tests: passed - HGraph and pruning regressions passed with 22 assertions and no TSAN diagnostics.
• TSAN functests '(PR) HGraph Search with Dirty Vector': passed - 283 assertions passed with no TSAN diagnostics.
• ASAN/UBSAN focused build and unit tests: passed - Both test binaries built; 22 focused assertions passed.
• ASAN/UBSAN functests '(PR) HGraph Search with Dirty Vector': passed - 283 assertions passed; the prior heap-buffer-overflow no longer occurs.

Residual Risks

• Native AArch64 execution was unavailable; the reported fault path was reproduced and verified under x86_64 ASan/UBSan.
• The trusted parent process must update the pull-request status label.

Base branch: 0.18

Fixes #2801

Updated by vsag-bot following maintainer direction from @wxyucs.

[vsag-bot]

/label status/waiting-for-review
/waiting-on reviewer
/request-review @wxyucs
/request-review @inabao
/request-review @ShawnShawnYou

[vsag-bot]

AI PR state: completed
Current owner: unassigned
Reason: PR state is closed
Head: ac61bba

Automatic merging is disabled. A maintainer performs the final merge.

[mergify]

Merge Protections

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🟢 Require linked issue for feature/bug PRs

• body~=(?im)(?:^|[\s\-\*])(?:close[sd]?|fix(?:e[sd])?|resolve[sd]?)\s*:?\s+(?:#\d+|[\w.\-]+/[\w.\-]+#\d+|https?://github\.com/[\w.\-]+/[\w.\-]+/issues/\d+)

[LHT129]

Thanks for this fix. The change is clean and correct.

Summary of the fix:

• Three call sites in hgraph.cpp (KnnSearch, RangeSearch, SearchWithRequest) now guard result->Top() with not result->Empty() when descending route graph layers, preventing dereference of an empty result heap caused by non-finite distance filtering (e.g. all-NaN queries).
• A regression test in hgraph_add_test.cpp exercises the all-NaN query path and verifies the search returns an empty result set rather than crashing.

Review notes:

• The fix is minimal and surgical — exactly what a bug fix should be.
• When all route graph layers return empty, search_param.ep retains its initial value (entry_point_id_), which is already validated against INVALID_ENTRY_POINT before the loop. This is correct fallback behavior.
• The test case is well-scoped: deterministic, self-contained, and directly targets the reported crash path.
• No correctness, performance, or security concerns found.

[vsag-bot]

AI PR CI recovery

Item	Value
Status	rerun-requested
Head	ac61bba
Workflow	Tsan Build & Test Parallel
Classification	unrelated_transient
Confidence	98%
Action	Requested a rerun of failed jobs

The failure is unrelated to the pull request. Rerun the same workflow; no repository changes were made.

Reasoning:
The PR changes only HGraph, Pyramid, pruning, and associated tests. It does not modify CI, CMake, Makefiles, external dependencies, or Docker configuration. CI failed while independently building the pinned OpenBLAS 0.3.23 dependency at step 39/1056, before any changed translation unit was reported. The Git ownership and Node.js messages were nonfatal warnings. Although the omitted OpenBLAS sub-log prevents identifying the precise runner fault, the dependency boundary establishes that this was not caused by the PR diff.

[codecov]

Codecov Report

❌ Patch coverage is 96.29630% with 1 line in your changes missing coverage. Please review.

@@            Coverage Diff             @@
##             0.18    #2802      +/-   ##
==========================================
- Coverage   91.84%   91.76%   -0.08%     
==========================================
  Files         335      335              
  Lines       20078    20089      +11     
==========================================
- Hits        18440    18435       -5     
- Misses       1638     1654      +16     

Flag	Coverage Δ
cpp	91.76% <96.29%> (-0.08%)	⬇️

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

Components	Coverage Δ
common	86.03% <ø> (-0.18%)	⬇️
datacell	93.20% <ø> (-0.37%)	⬇️
index	91.73% <95.83%> (-0.06%)	⬇️
simd	100.00% <ø> (ø)

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[wxyucs]

@vsag-bot This PR remains labeled status/ai-working, but Build with TSAN and Test Aarch64 (functests) are still failing and there has been no update since August 28. Please inspect the current failures and continue advancing the PR.

[wxyucs]

@vsag-bot Please resume this PR. The current head still has failures in Build with TSAN (https://github.com/antgroup/vsag/actions/runs/33160117157/job/98812268706) and Test Aarch64 (functests) (https://github.com/antgroup/vsag/actions/runs/33160117244/job/98841395297). Please inspect the logs, address repository defects, and update the status label to reflect the actual progress or blocker. Review threads are resolved and GitHub currently reports no conflicts.

[vsag-bot]

AI PR continuation

Item	Value
Status	branch-updated
Requested by	@wxyucs
Direction	Maintainer comment
Base	0.18 (latest at checkout)
Branch	codex/ai-fix-2801-2ff00610
Previous head	261072f
Updated head	ac61bba

I rebuilt the work on the latest base, pushed the remaining fix, and CI will run for the updated head.

Summary:
Fixed search- and construction-time empty candidate handling. The previously reproducible ASan overflow and dirty-vector result regression now pass under ASan/UBSan and TSAN.

Root cause:
Non-finite vectors can leave route-search and graph-construction candidate heaps empty. HGraph dereferenced those heaps, pruning accessed an empty neighbor vector, and disconnected dirty nodes could replace valid graph entry points.

Changes:

• Guarded empty route results in KNN, range, request, and construction descent paths.
• Made mutual connection safely represent an empty candidate set.
• Prevented disconnected nodes from replacing HGraph and Pyramid entry points.
• Restored all newly created HGraph route levels after an unconnectable insertion.
• Added deterministic dirty-vector addition/search and empty-pruning regressions.

Validation:

Command	Result	Detail
clang-format-15 --dry-run --Werror <changed C++ files> && git diff --check	passed	Formatting and whitespace checks passed.
cmake --build build-tsan-ai-clean --parallel 4	passed	Complete TSAN build passed; final affected sources and targets rebuilt successfully.
TSAN focused unit tests	passed	HGraph and pruning regressions passed with 22 assertions and no TSAN diagnostics.
TSAN functests '(PR) HGraph Search with Dirty Vector'	passed	283 assertions passed with no TSAN diagnostics.
ASAN/UBSAN focused build and unit tests	passed	Both test binaries built; 22 focused assertions passed.
ASAN/UBSAN functests '(PR) HGraph Search with Dirty Vector'	passed	283 assertions passed; the prior heap-buffer-overflow no longer occurs.

Residual risks:

• Native AArch64 execution was unavailable; the reported fault path was reproduced and verified under x86_64 ASan/UBSan.
• The trusted parent process must update the pull-request status label.

[wxyucs]

@vsag-bot Thanks for updating the branch. Fresh CI on ac61bba now fails in the bundled OpenBLAS build, including ASan X86 (https://github.com/antgroup/vsag/actions/runs/35213407162/job/105176092608) and Lint (https://github.com/antgroup/vsag/actions/runs/35213407034/job/105177637281); the lint job failed during its prerequisite build, not an identified clang-tidy finding. TSan build also failed (https://github.com/antgroup/vsag/actions/runs/35213406968/job/105179288229). Please inspect detailed dependency logs and continue. Related historical tracking: #2507; #2971 is a 1.0 dependency repair, not proof of the same cause on 0.18. Do not assume an OOM or CPU-detection cause without evidence, or change HGraph code merely to address an unrelated dependency failure.

[wxyucs]

@vsag-bot Following up on the outstanding dependency-build failures: this PR still has the same head and failed ASan/Lint/TSan builds after the previous continuation request. Please inspect the OpenBLAS detailed logs, determine whether a scoped dependency fix/backport is needed on 0.18, and update the status label with the actual blocker. The 1.0 dependency fix #2971 has merged, but its applicability to these failures must be verified rather than assumed. Do not change HGraph behavior to hide an unrelated build failure.