pgvector_hnsw: parallel HNSW index build (hnswbuild.c HnswBeginParallel) on the pgrust parallel context - #98
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Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
- Remove PgError from file-scope imports; import it only in test module - Move HnswTypeInfo block comment to correct location (was attached to HnswNormalizeFn) - Add short one-line doc comments for the two type aliases Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
…fault) Add l2_normalize_image function to normalize vectors to unit L2 norm, handling zero vectors correctly by leaving them unchanged. Add VECTOR_TYPE_INFO static initialized with the default HnswTypeInfo for vector opclasses: max_dimensions from types_hnsw, l2_normalize as the normalize function, and no check_value proc. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
…Info) form_index_value / get_scan_value / max_dimensions now go through the type info instead of the vector-only paths; no behaviour change for the vector opclasses (no proc 3 -> VECTOR_TYPE_INFO). Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Make form_index_value_runs_check_value_before_norm_gate discriminating by using the zero vector (norm == 0) instead of (3,4): under the correct C order (checkValue before the norm gate) the checkValue error must surface, whereas a swapped order would return Ok(None) first and fail the assertion. Add a companion test proving the norm gate itself still rejects the zero vector when type_info has no check_value (the real vector-opclass default). Also drop the redundant `use types_hnsw::HnswTypeInfo;` already covered by the pre-existing `use types_hnsw::*;` glob in utils.rs. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
…d divergence notes InitBuildState in C (hnswbuild.c) calls HnswGetTypeInfo, then the dimensions/ef_construction checks, and only then HnswInitSupport (the source of "missing support function 1 ..."). init_build_state called init_support (which resolves type info internally) first, inverting that error precedence; now it resolves type info directly for the checks and defers init_support until after them. get_type_info reinterpreted proc 3's Datum as a pointer with no null check and a SAFETY comment that asserted trust rather than describing C's actual (unchecked) contract; added a null check raising ERRCODE_INTERNAL_ERROR and rewrote the comment to describe that contract and its limits. Recorded two more divergences in pgvector_hnsw's module doc: normalize callbacks take no collation (unused by every shipped implementation), and vacuum now also resolves/calls proc 3 via init_support since C's hnswvacuum only calls HnswInitSupport. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Trivial cleanup: drop a double blank line in vec.rs, remove a redundant HnswTypeInfo import and split double-statement/overlong lines in insert.rs's type_info_tests, and annotate the norm/normalize .expect() sites in insert.rs and scan.rs with why C would never hit them. Also rewrites the regression harness README: it previously claimed "all shipped features" for an argument-less run, but on this tree halfvec/sparsevec and the btree/cast/copy paths that depend on them aren't ported yet, so those upstream tests fail by design (they're the acceptance criteria for the follow-up PRs) and a full run exits non-zero. Documents the mktemp -d diff directory on FAIL and that this harness runs the unmodified upstream suite, distinct from the trimmed in-repo smoke tests under crates/contrib/pgvector/sql/. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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Included review availability: Your plan provides up to 8 included reviews per hour; 4 remain after this review. 📝 WalkthroughWalkthroughThe change adds HNSW type metadata and callbacks, a shared concurrent graph, graph-page flushing, parallel HNSW builds, caller-provided index scans, seam registration, and an upstream pgvector regression harness. ChangesHNSW build implementation
Estimated code review effort: 5 (Critical) | ~120 minutes Merge Risk: 🟡 Moderate · up to Parallel HNSW index building adds concurrent graph construction and scanning, but invalid custom operator-class metadata may crash a backend and failed build callbacks may leave scan resources uncleared. These failure paths should be fixed before merge. Sequence Diagram(s)sequenceDiagram
participant build_index
participant build_graph
participant parallel_build
participant SharedGraph
participant flush_pages
build_index->>build_graph: start HNSW index build
build_graph->>parallel_build: select workers and begin scan
parallel_build->>SharedGraph: insert heap tuples
parallel_build->>flush_pages: complete scan
flush_pages->>SharedGraph: serialize graph and clear state
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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In `@crates/backend/executor/execindexing/src/build_scan.rs`:
- Line 180: Update table_index_build_scan_with so HeapScanDescData is closed
with heapam::heap_endscan(scan) on every return path, including errors
propagated by ?. Preserve the original error while ensuring cleanup occurs
before propagation.
In `@crates/contrib/pgvector_hnsw/src/scan.rs`:
- Line 135: Update l2_normalize_image around the normalize call to validate the
input vector for infinite values before normalization, restoring rejection with
the existing “value out of range: overflow” error. Preserve the current output
validation and normal successful normalization behavior.
In `@crates/contrib/pgvector_hnsw/src/utils.rs`:
- Line 92: Validate HNSW opclass support procedure 3 before get_type_info can
consume its result: whitelist only repository-owned static HnswTypeInfo
providers in hnswvalidate and the HNSW member-adjustment path, or reject
procedure 3 entirely until such a registry exists. Ensure untrusted nonzero or
transient Datum values cannot be cast and dereferenced as &'static HnswTypeInfo.
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crates/_support/seams_init/Cargo.tomlcrates/_support/seams_init/src/lib.rscrates/_support/types/types_hnsw/src/lib.rscrates/backend/access/nbtree/nbtsort/src/pool.rscrates/backend/executor/execindexing/Cargo.tomlcrates/backend/executor/execindexing/src/build_scan.rscrates/backend/executor/execindexing/src/lib.rscrates/contrib/pgvector/Cargo.tomlcrates/contrib/pgvector/src/vec.rscrates/contrib/pgvector/test/README.mdcrates/contrib/pgvector/test/pgvector-regress.shcrates/contrib/pgvector_hnsw/src/insert.rscrates/contrib/pgvector_hnsw/src/lib.rscrates/contrib/pgvector_hnsw/src/scan.rscrates/contrib/pgvector_hnsw/src/utils.rscrates/contrib/pgvector_hnsw_build/Cargo.tomlcrates/contrib/pgvector_hnsw_build/src/algo.rscrates/contrib/pgvector_hnsw_build/src/flush.rscrates/contrib/pgvector_hnsw_build/src/graph.rscrates/contrib/pgvector_hnsw_build/src/lib.rscrates/contrib/pgvector_hnsw_build/src/parallel.rs
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…p output Review follow-ups on the harness script: - Discover tests with a glob into a bash array instead of word-splitting `ls` output (SC2046), and exit 2 with "no tests selected" when the selection is empty instead of printing "all selected tests passed" over zero tests. - Create the output directory before installing the EXIT trap and remove it from the trap when every test passed; a failing run keeps it (the FAIL line names the diff), and -k keeps both it and the database. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Adds graph.rs with the thread-shared in-memory HNSW graph data structures for the P3 parallel HNSW build: SharedGraph, SharedElement, Candidate, NeighborArray, Placement, HeapTids. Mirrors pgvector 0.8.5's HnswGraph/HnswElementData (hnsw.h), but replaces the C DSM area + per- element LWLock with an Arc-slice behind a RwLock and per-field Mutexes, since worker threads here are OS threads sharing one address space rather than separate processes over shared memory. lib.rs only gains the `pub(crate) mod graph;` declaration; the existing Graph/MemElement types are untouched until Task 2 replaces them. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
…s entry/element lock protocol Port hnswbuild.c's InsertTupleInMemory / UpdateGraphInMemory / UpdateNeighborsInMemory / FindDuplicateInMemory and the in-memory arm of hnswutils.c's HnswFindElementNeighbors / HnswSearchLayer / SelectNeighbors / HnswUpdateConnection from the serial bump-arena Graph onto the thread-shared SharedGraph, reproducing pgvector's lock protocol: entryWaitLock acquire+release -> drop(lk(&graph.entry_wait_lock)) entryLock LW_SHARED -> graph.entry_lock.read() upgrade (level > ep->level) -> drop read; entry_wait_lock; entry_lock.write(); drop wait e->lock LW_SHARED + memcpy -> copy of neighbors[layer].items under the element mutex neighborElement->lock EXCL -> neighbor's mutex held across update_connection dup->lock LW_EXCLUSIVE -> dup's heaptids mutex in find_duplicate Only one nesting exists (element mutex -> arena read lock, via elem()), and alloc_element takes the arena write lock while holding no element lock, so the order cannot cycle. lib.rs keeps the serial build working on the new graph: BuildState.graph is an Arc<SharedGraph>, insert_tuple allocates through alloc_element, and the flush path reads elements through elem()/neighbors/placement. The flush head list is taken once and shared by CreateGraphPages and WriteNeighborTuples. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
- algo.rs update_neighbors: replace the mem::take + write-back pattern with two disjoint field borrows of the same NeighborArray, so a panic inside update_connection can never leave an empty neighbor list behind after poison recovery. - graph.rs: record in DIVERGENCES that memory accounting now charges size_of::<SharedElement>() (vs the pre-refactor MemElement), so the flush point and the maintenance_work_mem notice's tuple count differ from both the pre-refactor Rust and from C. - algo.rs four-thread test: make generated values distinct across threads and iterations (index-derived base value plus a sub-gap hash jitter) so the "entry point has max level" assertion cannot flake on a duplicate holding the strict max level. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Move create_meta_page, build_append_page, serialize_element_tuple, serialize_neighbor_tuple, page_add, create_graph_pages, write_neighbor_tuples and flush_pages out of lib.rs into their own flush.rs module. Behavior is unchanged except flush_pages now takes graph.entry_wait_lock then graph.entry_lock for write (the same upgrade dance insert_tuple_in_memory uses) before walking the graph, holding the write lock through clear_after_flush(); the caller (insert_tuple) never holds entry_lock when it calls flush_pages, so this cannot deadlock. The flush_lock wrapper around the flush decision itself is left for a later task. Added a TDD-first test (flush::tests:: flush_serialization_matches_live_neighbor_state) that builds a 50-element 1-D graph through insert_tuple_in_memory, assigns synthetic placements the way create_graph_pages would, and asserts the neighbor tuple's valid (non-placeholder) entries equal the live neighbors.lock()[0].items.len(). Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
…scan's scan argument) Add a trailing Option<tableam::TableScanDesc> parameter down through table_index_build_scan_with -> table_index_build_range_scan_with_xmin, mirroring C's heapam_index_build_range_scan: a caller-supplied scan is used as-is (no range restriction, asserted start_blockno == 0 && numblocks == InvalidBlockNumber), no fresh snapshot is registered (need_unregister_snapshot stays false; the scan's own snapshot governs visibility), and it is still ended via heap_endscan before returning. table_index_build_scan and table_index_build_range_scan pass None, reproducing prior behaviour exactly. nbtsort's morsel_body, the only other caller of table_index_build_range_scan_with_xmin in the workspace, is updated to pass None for the new parameter. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Critical: table_index_build_scan_with was never added to lib.rs's
`pub use build_scan::{...}` list, so no other crate could actually call
it — the whole point of the task. Add it.
Minor: document the precondition that a caller-provided scan must be
tableam::TableScanDesc::Heap (a Pgrcolumnar scan panics), matching the
function's existing invariant-documentation style.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Ports hnswbuild.c's parallel machinery (HnswBeginParallel, HnswParallelBuildMain, HnswParallelScanAndInsert, ParallelHeapScan, HnswEndParallel, ComputeParallelWorkers, BuildGraph) plus InsertTuple's flushLock protocol. * graph.rs: flush_lock becomes an RwLock — held SHARED across an in-memory insert and EXCLUSIVE around the flush decision, so no flush can start while a participant is inserting. memory_exhausted takes C's memoryMargin (1MB in a parallel build, 0 serial). * parallel.rs: HnswShared (Arc-shared graph + parallel scan descriptor + the workersdonecv/nparticipantsdone counters), the leader's begin_parallel/parallel_heap_scan/end_parallel, the per-participant parallel_scan_and_insert, the HnswParallelBuildMain worker entry, and compute_parallel_workers over the planner's log3 worker arithmetic. * lib.rs: insert_tuple follows C's flushLock protocol; build_graph drives the parallel or serial scan, flushes, then ends the parallel build (C's order); init_seams registers the worker entrypoint. The leader's wait loop uses a bounded condvar wait that also drains parallel messages and probes worker liveness, so a worker that ERRORs surfaces its error instead of wedging the leader (C relies on a dying worker process implicitly waking the ConditionVariable). Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
SharedGraph::elem() took the `elems: RwLock<Vec<Arc<SharedElement>>>` read lock and cloned/dropped an Arc on every call — two contended atomics per lookup, O(ef_construction * m) lookups per insert, on cache lines every participant touches (the entry point and other hubs above all). Task 5 measured the consequence: 2 workers bought 5-10% over serial where three independent serial builds scale near-linearly on the same box. Replace the arena with C's shape: an append-only chunked arena. A chunk directory of `AtomicPtr<Chunk>` sized once in new() from memory_total, 1024 `MaybeUninit<SharedElement>` slots per chunk, a published `len: AtomicU32`, and an `alloc_lock: Mutex<()>` taken only by alloc_element (C serialises allocation under graph->allocatorLock too). alloc_element writes the element into its slot and publishes `len` with Release; elem(id) is an Acquire load of the chunk pointer plus an index and returns `&SharedElement` — no lock, no refcount. Slots below len are initialized, never moved (chunks are fixed-size blocks, the directory is never resized) and never freed before Drop, which needs &mut self and so cannot run under an outstanding borrow; Drop drops the initialized slots and frees the chunks. clear_after_flush now resets only the logical graph (length via a `cleared` flag, head, entry point) and keeps the storage until the graph is dropped — recorded as a DIVERGENCE from C's graphCtx reset, with the memory consequence. memory_exhausted also reports exhaustion when the directory runs out (only reachable above ~40GB maintenance_work_mem), so the build flushes rather than overrunning the arena. algo.rs call sites take &SharedElement and fetch each element once: search_layer reads a neighbor's distance and level off one reference, check_element_closer one lookup per r element per call. C's control flow is otherwise unchanged. Measured (100k x 128-dim, m=16, ef_construction=64, maintenance_work_mem=64MB): serial 80.8s, 2 workers 28.0s, 4 workers 18.2s. On Task 5's 50k x 16-dim case, where Task 5 measured serial 9.45s / 2 workers 8.63s / 4 workers 8.68s: 7.15s / 2.47s / 1.52s. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
* compute_parallel_workers: C's compute_parallel_worker takes the `rel_parallel_workers != -1` branch BEFORE the size gate, so a table with the parallel_workers reloption set builds in parallel even below min_parallel_table_scan_size. Restore that order (factored into workers_for_heap, with a unit test) and correct the DIVERGENCES header, which claimed the gate always applied. * compute_parallel_workers: return 0 when the heap's table AM is not heap — this lane scans through table_index_build_scan_with, which is heap-only in pgrust, so a columnar heap would previously panic inside it. Recorded as a DIVERGENCE. * parallel.rs module header: state the teardown contract — refusal paths unregister the snapshot, destroy the context and leave parallel mode; after a successful launch, errors rely on AtEOXact_Parallel / resource-owner cleanup, as C does via its longjmp to the abort path. * build_graph: drop the dead `bs.memory_margin = PARALLEL_MEMORY_MARGIN` on the outer BuildState — the leader's inserts run through the participant BuildState that parallel_scan_and_insert builds. * parallel_heap_scan: wait_timeout 20ms -> 100ms; the condvar notify is the real wake and the timeout is only the liveness safety net. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
…arena
Whole-branch review follow-ups on the in-memory graph:
- graph.rs header: record that the memory budget is tested outside the
allocator lock. C InsertTuple (hnswbuild.c:524-537) holds
graph->allocatorLock EXCLUSIVE across the memoryUsed + memoryMargin >=
memoryTotal test AND the element/value allocation, so the check is exact;
here memory_exhausted() is a Relaxed load outside alloc_lock and
memory_used.fetch_add runs before alloc_lock is taken, so the budget can
be overshot by at most (participants x one element) -- far below the 1MB
parallel margin -- and the re-check under flush_lock.write() keeps
multi-participant exhaustion correct. One-line note at the fetch_add too.
- Capacity headroom. dir_len_for's .clamp(1, MAX_CHUNKS) can discard the
two spare chunks, and memory_exhausted's old `len >= capacity` clause
fired exactly at len == capacity while N racing participants could still
reach alloc_element's assert!. memory_exhausted now treats
len + CHUNK_SIZE > capacity as exhausted (a full chunk of headroom), and
alloc_element's assert! becomes a debug_assert plus a graceful
PgError::error("hnsw graph arena is full") -- signature is now
PgResult<u32>, propagated in insert_tuple -- so even the >40GB regime
degrades to the on-disk path instead of panicking a backend. New unit
test drives both clauses to their boundary.
- elem(): the SAFETY argument lived only in the doc comment; state it on
the unsafe block itself.
- Per-field docs for entry_lock / entry_wait_lock naming their C protocol
(hnswbuild.c InsertTupleInMemory 453-470: wait-lock ping, shared entry
lock, exclusive upgrade when the new element's level exceeds the entry
point's).
- len() is a tests-only accessor (no progress reporting reads it).
- flush.rs module header: the flush_lock wrapper exists now, so state the
actual contract -- flush_pages runs either under flush_lock.write() from
insert_tuple or from build_graph/build_index with no other participant
live, and its own entry_wait_lock + entry_lock.write() are a deliberate
superset of C FlushPages (which takes no locks and relies on the caller's
flushLock), leaving no caller-side entry-lock precondition.
- serialize_element_tuple / serialize_neighbor_tuple are private; the
child test module still sees them.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
table_index_build_scan_with's caller-provided-scan arm panicked when the
TableScanDesc was not a heap scan. Raise ERRCODE_FEATURE_NOT_SUPPORTED
("table_index_build_scan_with: only heap scans are supported") instead --
a backend must not panic on a reachable-by-typing input -- and say so in
the doc comment rather than documenting a panic.
Also put the tableam dev-dependency back where it was; it is additionally
a real dependency now (build_scan matches on tableam::TableScanDesc in
non-test code), so the entry under [dependencies] stays and the move out
of [dev-dependencies] was diff noise.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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Summary
Ports pgvector 0.8.5's parallel HNSW index build (
hnswbuild.c:HnswBeginParallel,HnswParallelBuildMain,HnswParallelScanAndInsert,ParallelHeapScan,HnswEndParallel,ComputeParallelWorkers) onto pgrust's parallel-context API.CREATE INDEX ... USING hnswnow honoursmax_parallel_maintenance_workers(and theparallel_workersreloption) like C. Built on top of #95 (merged in as the base of this branch).max_parallel_maintenance_workers = 0)For reference, native PostgreSQL 18 + pgvector 0.8.6 on the same machine builds the same index in 20.5 s with 2 workers (56.7 s serial).
Design
C keeps the in-memory graph in a DSM segment with relative pointers and an LWLock per element. Here the graph is a thread-shared
SharedGraphinpgvector_hnsw_build:graph.rs): append-only chunked storage (AtomicPtr<Chunk>directory, 1024 slots per chunk,lenpublished with Release);elem(id)is an Acquire load plus an index, no lock, no refcount. Allocation is serialized by a small mutex (C:allocatorLock). Per-elementMutexes guard neighbor lists / heaptids exactly where C holds the element's LWLock.algo.rs): C'sInsertTupleInMemoryline by line —entryWaitLock/entryLockdance with the exclusive upgrade when the new element's level exceeds the entry point's, neighbor lists copied out under the owner's lock, each neighbor updated under its own lock, duplicates appended to the existing element and never added to the head list.lib.rs,flush.rs):flushLockas anRwLockheld shared across the whole in-memory insert and exclusive aroundFlushPages(CInsertTuple510-574),memoryMarginof 1 MiB when parallel.parallel.rs):HnswShared(oids, concurrency flag, done counter + condvar, parallel block-scan descriptor, the graph, build parameters) published via the parallel context's private slot; the leader participates, then waits fornparticipantsdone == nlaunched + 1while draining worker messages so a worker error surfaces instead of hanging;WaitForParallelWorkersToFinish→ snapshot unregister →DestroyParallelContext→ExitParallelMode. Workers open the relations with C's lock modes (incl.CONCURRENTLY), build their ownHnswSupport(FmgrInfois notSend), join the parallel heap scan through a newexecindexing::table_index_build_scan_with(scan)(C's trailingscanargument) and insert into the shared graph. Every refusal (no workers configured, none launched) falls back to the serial build on the same graph.One implementation serves serial and parallel builds (C switches on
base == NULL); the serial path's behaviour is unchanged (hnsw_vector.sqlbyte-identical, serial timing unchanged).Lock order (acyclic, checked at every acquisition site):
flush_lock(RwLock) →entry_wait_lock(Mutex) →entry_lock(RwLock) → per-element mutexes (neighbors,heaptids,placement) /alloc_lock/head/entry_point.update_connectionruns under one neighbor's mutex and reads only immutable values, so element mutexes never nest. Arena happens-before: an element id crosses threads only through mutex-protected containers (entry point, neighbor lists, head list) or thelenAcquire load, each of which synchronizes with the publisher's Release after the slot is written; slots are never moved or freed before the graph is dropped, soelem(id) -> &SharedElementneeds no lock.Recorded divergences
graphCtxat flush), so peak RSS during the on-disk phase is up tomaintenance_work_memhigher than C's.allocatorLockacross check + allocation); the budget can be overshot by at most one element per participant, well inside the 1 MiB parallel margin, and the flush decision is re-checked under the exclusive flush lock.plan_create_index_workersis not ported: expression/predicate indexes build serially (noPlannerRunforis_parallel_safe); there is no 32 MB-per-participantmaintenance_work_memfloor; theparallel_workersreloption bypasses themin_parallel_table_scan_sizegate as in C."postgres"(the pgrust worker lookup panics on any other name).pgstat_progress_update_param) is not ported, as before.Verification
cargo test --release -p pgvector_hnsw_build(arena publication/chunk-boundary, 8-writer/4-reader race, 4-thread insert invariants, worker-count log3 rule, flush serialization)cargo build --release --locked --bin postgreshnsw_vector,vector_typemaintenance_work_mem = 4MB+ 2 workersCREATE INDEX CONCURRENTLYwith workersDROP INDEX🤖 Generated with Claude Code
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