Remove vestigial code left from removed hasher variants: unused
BuildHasherDefault import, PhantomData suppression line, orphan planning
comments for Variant C/E. Also drop an unused `mut` on the PRNG closure
binding. No behavior change; compiles warning-free.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The BFS in execute_expand emits one (src_idx, dst_id) pair per edge, so
dst_id_list contains heavy duplication when multi-hop traversals revisit
the same destination nodes. hydrate_nodes then built an
"id IN ('a', 'b', ...)" filter from the full list, passing it verbatim
to Lance. On a 30k-node Person graph, a 3-hop query produced a 15.4M-
entry IN-list against a 30k-row target — 512x more entries than unique
ids.
Deduplicate before the Lance scan; the post-hydrate alignment HashMap
already fans results back out to the original (src, dst) pairs, so
output is bit-identical.
Bench numbers (crates/omnigraph/examples/bench_expand.rs, min of 2-3
runs, release build):
query before after speedup
1k hop3 460 ms 28 ms 16x
10k hop2 4.21 s 188 ms 22x
10k hop3 40.59 s 1.30 s 31x
30k hop2 11.71 s 678 ms 17x
30k hop3 197.38 s 4.86 s 41x
All existing omnigraph-engine tests pass (72/72, 0 failures).
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
