fix(tests): assert exact ANN index name and ensure index creation in test_the_kill_switch_flips_real_retrieval_depth (#3619)

[Sanderhoff-alt]

Overview

Fixes #3619.

test_ann_iterative_scan.py::test_the_kill_switch_flips_real_retrieval_depth previously relied on a brittle proxy assertion ("Index Scan" in plan and "Sort" not in plan) to check if the query was served by an ANN index. In environments where the per-bank vector index was not created eagerly (e.g. HINDSIGHT_API_VECTOR_INDEX_MIN_ROWS > 0), PostgreSQL had no viable ANN candidate and fell back to B-tree indexes + a disabled Sort node, failing the test.

This PR makes the test robust by ensuring the per-bank vector index is explicitly created regardless of threshold configuration and asserting the execution plan against the exact deterministic index name (idx_mu_emb_worl_<internal_id>).

---

Execution Flow & Lifecycle

flowchart TD
    A[Start Test] --> B[Create Bank Profile]
    B --> C[Fetch internal_id from banks table]
    C --> D[Explicitly create per-bank vector index idx_mu_emb_worl_uid]
    D --> E[Insert 600 Fact Rows & Run ANALYZE]
    E --> F[Run EXPLAIN Query with disabled seqscan & sort]
    F --> G{Plan Verification}
    G -->|Contains idx_mu_emb_worl_uid & No Sort| H[Execute retrieve_semantic_bm25_combined_sql]
    G -->|Missing index or contains Sort| I[Fail with explicit assertion message]
    H --> J[Assert with_resume == 400 and without_resume <= 250]

Loading

---

Comparative Analysis (Before vs After)

Dimension	Before (Issue #3619)	After (This PR)
Index Guarantee	Implicitly relied on eager bank index creation (VECTOR_INDEX_MIN_ROWS=0). When lazy index thresholds were set, the bank had no vector index.	Explicitly invokes ops.create_bank_vector_indexes on test setup, guaranteeing idx_mu_emb_worl_<internal_id> exists across all configurations.
Plan Assertion	Weak proxy: "Index Scan" in plan and "Sort" not in plan. Any of ~19 B-tree indexes could match "Index Scan".	Precise assertion: assert index_name in plan and assert "Sort" not in plan.
Failure Diagnostics	Obscure failures reporting irrelevant B-tree indexes (e.g., idx_memory_units_fact_type + Sort).	Clear assertion failures identifying missing ANN index or unexpected fallback nodes.
Environment Decoupling	Fails when HINDSIGHT_API_VECTOR_INDEX_MIN_ROWS > 0.	Decoupled; passes in both default and threshold-configured test runs.

---

Changes Summary

File	Change	Description
hindsight-api-slim/tests/test_ann_iterative_scan.py	Modify	1. Import _BANK_INDEX_FACT_TYPES, _bank_index_name, _vector_index_clause. 2. Query internal_id and call memory._backend.ops.create_bank_vector_indexes during setup. 3. Assert index_name in plan and "Sort" not in plan.

---

Verification Matrix

Test Case	Environment / Configuration	Result
test_the_kill_switch_flips_real_retrieval_depth	Default configuration (VECTOR_INDEX_MIN_ROWS=0)	PASSED (1 passed)
test_the_kill_switch_flips_real_retrieval_depth	Threshold mode (HINDSIGHT_API_VECTOR_INDEX_MIN_ROWS=10000, previously 100% failing)	PASSED (1 passed)
tests/test_ann_iterative_scan.py (all tests)	Default configuration	PASSED (11/11 passed)
Code Quality & Static Typing	ruff check, ruff format --check, ty check, lint.sh	PASSED (clean)

Fixes #3619

[strix-security]

Strix Security Review

No security issues found.

_{Updated for 4afc7d7.}

---

Reviewed by Strix
_{Re-run review · Configure security review settings}