From 5bef2f4d860976d70e6a6560c1469445dbc501a8 Mon Sep 17 00:00:00 2001
From: nnethercott <nathaniel@deepomatic.com>
Date: Mon, 15 Sep 2025 16:10:56 +0200
Subject: [PATCH] Update arroy-hannoy conversion internals

---
 crates/milli/src/vector/store.rs | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/crates/milli/src/vector/store.rs b/crates/milli/src/vector/store.rs
index d4d3f26cb..667d6b37d 100644
--- a/crates/milli/src/vector/store.rs
+++ b/crates/milli/src/vector/store.rs
@@ -1046,6 +1046,10 @@ impl VectorStore {
     where
         R: rand::Rng + rand::SeedableRng,
     {
+        // No work if distances are the same
+        if AD::name() == HD::name() {
+            return Ok(());
+        }
         for index in vector_store_range_for_embedder(self.embedder_index) {
             let arroy_reader: arroy::Reader<AD> =
                 match arroy::Reader::open(arroy_rtxn, index, self.database.remap_types()) {
@@ -1084,6 +1088,10 @@ impl VectorStore {
     where
         R: rand::Rng + rand::SeedableRng,
     {
+        // No work if distances are the same
+        if AD::name() == HD::name() {
+            return Ok(());
+        }
         for index in vector_store_range_for_embedder(self.embedder_index) {
             let hannoy_reader: hannoy::Reader<HD> =
                 match hannoy::Reader::open(hannoy_rtxn, index, self.database.remap_types()) {
@@ -1098,12 +1106,8 @@ impl VectorStore {
             arroy_writer.clear(arroy_wtxn)?;
             for entry in hannoy_reader.iter(hannoy_rtxn)? {
                 let (item, mut vector) = entry?;
-                // hannoy bug? the `vector` here can be longer than `dimensions`.
-                // workaround: truncating.
-                if vector.len() > dimensions {
-                    vector.truncate(dimensions);
-                }
-                // arroy and hannoy disagreement over the 0 value
+                debug_assert!(vector.len() == dimensions);
+                // arroy and hannoy disagreement over the 0 value if distance is Hamming
                 // - arroy does:
                 //     - if x >= 0 => 1
                 //     - if x < 0 => -1