Emit core HNSW index properties in extract summary

[tazarov]

Summary

• add index_properties to extract summaries with m, ef_construction, cur_element_count, max_elements, persisted_version, and word_size_bytes
• populate the new fields from parsed header.bin values during extraction
• expose the updated extract response shape in Go bindings and documentation
• add extractor tests for the new properties, including capacity/count assertions in property-based coverage

Validation

• cargo test
• cargo clippy --all-targets -- -D warnings
• go test ./...

[tazarov]

Addressed the review follow-ups in commit 5e1ff08:

• changed Go to unsigned ()
• added Go JSON deserialization coverage for /
• made Rust JSON casing explicit with
• narrowed Rust to (serialized from header word size bytes)

Validation rerun:

• cargo test
• cargo clippy --all-targets -- -D warnings
• go test ./...

[tazarov]

Addressed the review follow-ups in commit 5e1ff08:

• changed Go WordSizeBytes to unsigned type (uint32)
• added Go JSON deserialization coverage for ExtractResponse and index_properties
• made Rust ExtractIndexProperties JSON casing explicit with serde rename_all snake_case
• narrowed Rust word_size_bytes to u32 (serialized from header word size bytes)

Validation rerun:

• cargo test
• cargo clippy --all-targets -- -D warnings
• go test ./...

[tazarov]

@claude review

[claude]

Claude finished @tazarov's task in 1m 55s —— View job

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Code Review

• Gather context and read changed files
• Review Rust changes (src/extractor.rs, src/lib.rs)
• Review Go changes (hnswtoolbox.go, hnswtoolbox_test.go)
• Review documentation (README.md)
• Post final review

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Overall Assessment: ✅ Looks Good

The implementation is clean, correct, and focused. The index_properties contract is well-defined, types are properly aligned between Rust and Go, and test coverage is solid. A few minor observations follow.

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Rust (src/extractor.rs, src/lib.rs)

ExtractIndexProperties struct (extractor.rs:36-43):

• Field types correctly mirror PersistentHeader fields (m: u64, ef_construction: u64, persisted_version: i32)
• word_size_bytes: header.word_size.bytes() as u32 — the as u32 cast from usize is safe here since HeaderWordSize::bytes() can only return 4 or 8 (closed enum). No truncation risk.
• #[serde(rename_all = "snake_case")] on fields that are already snake_case is a no-op, but it makes the serialization contract explicit — good defensive practice.

cur_element_count in index_properties vs scanned in ExtractSummary (extractor.rs:147-149):

• index_properties.cur_element_count is a header snapshot taken before scanning begins, while scanned is incremented per-record. These will always be equal for a valid index. The property tests explicitly verify this relationship (prop_assert_eq!(summary.index_properties.cur_element_count, fixture_records.len() as u64)). This is correct and intentional.

Minor: No Deserialize on ExtractIndexProperties (extractor.rs:34):

• The struct only derives Serialize, not Deserialize. This is consistent with ExtractSummary and is correct for the producer role this struct fills. Worth noting if a future consumer (e.g., round-trip Rust tests) needs deserialization.

lib.rs: ExtractIndexProperties is properly re-exported at the crate root (lib.rs:10). ✓

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Go (hnswtoolbox.go, hnswtoolbox_test.go)

Type alignment (hnswtoolbox.go:47-54):

Go field	Go type	Rust type	Match
M	uint64	u64	✓
EfConstruction	uint64	u64	✓
CurElementCount	uint64	u64	✓
MaxElements	uint64	u64	✓
PersistedVersion	int32	i32	✓
WordSizeBytes	uint32	u32	✓

All JSON tag names match the Rust serde snake_case output. ✓

hnswtoolbox_test.go:

• Covers JSON deserialization roundtrip for all six new fields ✓
• Uses t.Fatalf for every assertion — this stops at the first failure rather than reporting all mismatches. Using t.Errorf for non-fatal assertions would give a fuller picture on failure, but this is a minor style point for a new-struct deserialization test.

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Documentation (README.md)

• New index_properties block is added to both the "What It Extracts" summary (README.md:23-30) and the example Response JSON (README.md:114-123) ✓
• Field list matches the struct definition exactly ✓

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Test Fixture Sanity (src/extractor.rs:941-1010)

The write_fixture_with_capacity function produces a 100-byte header (U64 word size), which is correctly detected as HeaderWordSize::U64 by PersistentHeader::from_bytes. The written values (m=4, ef_construction=100, word_size_bytes=8) are consistent with all test assertions. ✓