Batch add references functionality

src/Weaviate.Client.Tests/Integration/TestBatch.cs

@@ -1,4 +1,5 @@
 using Weaviate.Client.Models;
+using Weaviate.Client.Models.Vectorizers;
 
 namespace Weaviate.Client.Tests.Integration;
 
@@ -44,4 +45,84 @@ public async Task InsertMany(string key)
             data.Select(d => d.References.Sum(r => r.Value.Count)).Sum()
         );
     }
+
+    [Fact]
+    public async Task Test_Batch_ReferenceAddMany()
+    {
+        // Setup referenced collection ("To")
+        var refCollection = await CollectionFactory(
+            name: "To",
+            vectorConfig: Vector.Name("default"),
+            properties: [Property.Int("number")]
+        );
+        int numObjects = 10;
+
+        // Insert objects into the referenced collection and get their UUIDs
+        var refInsertResult = await refCollection.Data.InsertMany(add =>
+            Enumerable.Range(0, numObjects).ToList().ForEach(i => add(new { Number = i }))
+        );
+
+        Guid[] uuidsTo = [.. refInsertResult.Select(r => r.ID!.Value)];
+
+        // Setup main collection ("From") with a reference property
+        var collection = await CollectionFactory(
+            name: "From",
+            properties: [Property.Int("num")],
+            references: [Property.Reference("ref", refCollection.Name)],
+            vectorConfig: Vector.Name("default")
+        );
+
+        // Insert objects into the main collection and get their UUIDs
+        var fromInsertResult = await collection.Data.InsertMany(add =>
+            Enumerable.Range(0, numObjects).ToList().ForEach(i => add(new { Num = i }))
+        );
+
+        Guid[] uuidsFrom = [.. fromInsertResult.Select(r => r.ID!.Value)];
+
+        // First batch: each "From" object references the "To" object with the same index
+        var batchReturn1 = await collection.Data.ReferenceAddMany(
+            Enumerable
+                .Range(0, numObjects)
+                .Select(i => new DataReference(uuidsFrom[i], "ref", uuidsTo[i]))
+                .ToArray()
+        );
+        Assert.False(batchReturn1.HasErrors);
+
+        // Second batch: each "From" object references the first 3 "To" objects
+        var batchReturn2 = await collection.Data.ReferenceAddMany(
+            Enumerable
+                .Range(0, numObjects)
+                .Select(i => new DataReference(uuidsFrom[i], "ref", uuidsTo.Take(3).ToArray()))
+                .ToArray()
+        );
+        Assert.False(batchReturn2.HasErrors);
+
+        // Fetch objects with references
+        var objects = await collection.Query.List(
+            properties: ["num"],
+            references: [new QueryReference(linkOn: "ref")]
+        );
+
+        foreach (var obj in objects)
+        {
+            var num = (long)obj.Properties["num"]!;
+            var refObjects = obj.References["ref"];
+
+            // The first reference should match the corresponding "To" object's "number"
+            Assert.Equal(num, (long)refObjects[0].Properties["number"]!);
+            Assert.Contains(refObjects[0].ID!.Value, uuidsTo);
+
+            // There should be 4 references: 1 from the first batch, 3 from the second
+            Assert.Equal(4, refObjects.Count);
+
+            // The next 3 references should have "number" properties 0, 1, 2 (order sorted)
+            var refs = refObjects
+                .Skip(1)
+                .Take(3)
+                .Select(r => (long)r.Properties["number"]!)
+                .OrderBy(x => x)
+                .ToList();
+            Assert.Equal(new List<long> { 0, 1, 2 }, refs);
+        }
+    }
 }