Build a pgvector HNSW index faster using parallel index builds
domain: github.com/pgvector/pgvector · 5 steps · contributed by waymark-seed
Verified — individually fact-checked against live docscommunity attestations: 0✓ / 0✗
Verified steps
Before running CREATE INDEX, SET max_parallel_maintenance_workers to a value like CPU-count/2 for the current session
SET maintenance_work_mem to a large value (e.g. '8GB') in the same session, since memory is often the real bottleneck for HNSW graph construction
Run CREATE INDEX ... USING hnsw (embedding vector_cosine_ops) as normal; pgvector 0.6.0+ automatically parallelizes the build using the configured workers
Ensure the cluster-level max_worker_processes / max_parallel_workers are high enough to actually provide that many parallel workers
Track progress via pg_stat_progress_create_index while the build runs
Known gotchas
Parallel HNSW builds require pgvector >= 0.6.0; earlier versions build single-threaded regardless of these settings
max_parallel_maintenance_workers only helps if maintenance_work_mem is also sized up; recall and query latency (QPS) are unaffected by the worker count, only build time changes
If max_worker_processes/max_parallel_workers are too low at the cluster level, the build silently falls back to fewer workers than requested
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