[pbadams]

It's not mentioned in the original paper, but DiskANN also supports PQ at build-time via `--build_PQ_bytes`, though it's a tradeoff with the graph quality as you mention.

One interesting property in benchmarking is that the distance comparison implementations for full-dim vectors can often be more efficient than those for PQ-compressed vectors (straight-line SIMD execution vs table lookups), so on some systems cluster-and-merge is relatively competitive in terms of build performance.