Fix: disable parallel index build on QD and AO tables (#12)

[yjhjstz]

HNSW and IVFFlat manage their own parallel builds via plan_create_index_workers(), bypassing the guard in core's index_build() (catalog/index.c) that disables parallel index builds on the dispatcher and for AO tables.

On the QD, the coordinator's empty, never-analyzed copy of the table still gets a 10-page default size estimate, so parallel workers can be launched (e.g. with min_parallel_table_scan_size lowered). Those workers are forced to GP_ROLE_EXECUTE by ParallelWorkerMain() and inherit QE-only globals (ic_htab_size, numsegmentsFromQD) from the QD leader, where both are 0. The worker then crashes:

• assert builds: FailedAssertion("ht->size > 0") in initConnHashTable (contrib/interconnect/udp/ic_udpifc.c)
• non-assert builds: "cannot access table ... in current transaction" from the numsegments sanity check in cdbcat.c

Mirror the core guard in ComputeParallelWorkers() (hnsw) and AssignTuples() (ivfflat). Parallel builds on segments are unaffected: QE backends hand valid interconnect state to their workers, and each segment still uses parallel workers after this change.

Fixes #12

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Summary by CodeRabbit

• Bug Fixes
  • Disabled parallel index building in dispatcher environments where it is unsupported.
  • Prevented parallel index builds for Append-Optimized tables.
  • Improved index build stability by ensuring parallel workers are only used in supported scenarios.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: a027da64-e165-4eeb-9477-ff242cf9363d

📥 Commits

Reviewing files that changed from the base of the PR and between ba8a9b3 and 50c234f.

📒 Files selected for processing (2)

• src/hnswbuild.c
• src/ivfbuild.c

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📝 Walkthrough

Walkthrough

Parallel index builds for HNSW and IVFFlat now disable worker execution when running as a dispatcher or against append-optimized tables. HNSW imports Cloudberry role declarations, while IVFFlat applies equivalent eligibility checks before planning workers.

Changes

Parallel index-build guards

Layer / File(s)	Summary
HNSW worker eligibility src/hnswbuild.c	ComputeParallelWorkers returns zero workers for dispatcher roles and append-optimized tables, with the required Cloudberry declarations included.
IVFFlat worker eligibility src/ivfbuild.c	AssignTuples only plans and launches parallel workers when the heap exists, the backend is not a dispatcher, and the table is not append-optimized.

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

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: disabling parallel index builds on QD and AO tables.
Description check	✅ Passed	The description explains the bug, the fix, and includes the required issue reference and change log section.
Linked Issues check	✅ Passed	The changes address #12 by preventing HNSW parallel builds on the QD while preserving valid parallel builds on segments.
Out of Scope Changes check	✅ Passed	The ivfflat and AO-related guards are within the stated goal of mirroring the core parallel-build guard behavior.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing Touches

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[my-ship-it]

LGTM, thanks