From edca75457ec554e9c43bc4e4dcfaf482f87a1a5d Mon Sep 17 00:00:00 2001
From: Ragnor Comerford <hello@ragnor.co>
Date: Tue, 9 Jun 2026 17:18:24 +0200
Subject: [PATCH] fix(engine): restrict anti-join bulk fast path to one-hop
 expands
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bulk_anti_join_applies accepted any single Expand, but try_bulk_anti_join_mask
decides via the CSR has_neighbors one-hop existence check — wrong for multi-hop
negations. Require min_hops==1 && max_hops==1 in the predicate; anything else
falls to the slow path, whose inner Expand runs the real bounded traversal.
Turns the multi-hop regression green; one-hop anti-joins unchanged.
---
 crates/omnigraph/src/exec/query.rs | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/crates/omnigraph/src/exec/query.rs b/crates/omnigraph/src/exec/query.rs
index c5c0b12..5bc18f2 100644
--- a/crates/omnigraph/src/exec/query.rs
+++ b/crates/omnigraph/src/exec/query.rs
@@ -1558,8 +1558,15 @@ async fn hydrate_nodes(
 fn bulk_anti_join_applies(inner_pipeline: &[IROp], outer_var: &str) -> bool {
     matches!(
         inner_pipeline,
-        [IROp::Expand { src_var, dst_filters, .. }]
-            if src_var == outer_var && dst_filters.is_empty()
+        [IROp::Expand { src_var, dst_filters, min_hops, max_hops, .. }]
+            if src_var == outer_var
+                && dst_filters.is_empty()
+                // `has_neighbors` is a ONE-hop existence test, so the fast path
+                // is valid only for a single-hop expand. Multi-hop negations
+                // (e.g. `not { $p knows{2,2} $x }`) fall to the slow path, whose
+                // inner Expand runs the real bounded traversal.
+                && *min_hops == 1
+                && (*max_hops).unwrap_or(1) == 1
     )
 }