Add new milli::update:🆕:indexer::sharding module

crates/milli/src/update/new/indexer/mod.rs

@@ -36,6 +36,7 @@ mod guess_primary_key;
 mod partial_dump;
 mod post_processing;
 pub mod settings_changes;
+pub mod sharding;
 mod update_by_function;
 mod write;
 

crates/milli/src/update/new/indexer/sharding.rs

@@ -0,0 +1,22 @@
+// Copyright © 2025 Meilisearch Some Rights Reserved
+// This file is part of Meilisearch Enterprise Edition (EE).
+// Use of this source code is governed by the Business Source License 1.1,
+// as found in the LICENSE-EE file or at <https://mariadb.com/bsl11>
+
+use std::hash::{BuildHasher as _, BuildHasherDefault};
+
+pub struct Shards {
+    pub own: Vec<String>,
+    pub others: Vec<String>,
+}
+
+impl Shards {
+    pub fn must_process(&self, docid: &str) -> bool {
+        let hasher = BuildHasherDefault::<twox_hash::XxHash3_64>::new();
+        let to_hash = |shard: &String| hasher.hash_one((shard, docid));
+
+        let max_hash = self.others.iter().map(to_hash).max().unwrap_or_default();
+
+        self.own.iter().map(to_hash).any(|hash| hash > max_hash)
+    }
+}