langchain: Passthrough batch_size on index()/aindex() calls (#19443)

**Description:** This change passes through `batch_size` to
`add_documents()`/`aadd_documents()` on calls to `index()` and
`aindex()` such that the documents are processed in the expected batch
size.
**Issue:** #19415
**Dependencies:** N/A
**Twitter handle:** N/A

libs/langchain/langchain/indexes/_api.py

@@ -330,7 +330,7 @@ def index(
         # Be pessimistic and assume that all vector store write will fail.
         # First write to vector store
         if docs_to_index:
-            vector_store.add_documents(docs_to_index, ids=uids)
+            vector_store.add_documents(docs_to_index, ids=uids, batch_size=batch_size)
             num_added += len(docs_to_index) - len(seen_docs)
             num_updated += len(seen_docs)
 
@@ -544,7 +544,9 @@ async def aindex(
         # Be pessimistic and assume that all vector store write will fail.
         # First write to vector store
         if docs_to_index:
-            await vector_store.aadd_documents(docs_to_index, ids=uids)
+            await vector_store.aadd_documents(
+                docs_to_index, ids=uids, batch_size=batch_size
+            )
             num_added += len(docs_to_index) - len(seen_docs)
             num_updated += len(seen_docs)
 

libs/langchain/tests/unit_tests/indexes/test_indexing.py

@@ -20,7 +20,7 @@ from langchain_core.embeddings import Embeddings
 from langchain_core.vectorstores import VST, VectorStore
 
 from langchain.indexes import aindex, index
-from langchain.indexes._api import _abatch
+from langchain.indexes._api import _abatch, _HashedDocument
 from langchain.indexes._sql_record_manager import SQLRecordManager
 
 
@@ -1304,3 +1304,44 @@ async def test_aindexing_force_update(
         "num_skipped": 0,
         "num_updated": 2,
     }
+
+
+def test_indexing_custom_batch_size(
+    record_manager: SQLRecordManager, vector_store: InMemoryVectorStore
+) -> None:
+    """Test indexing with a custom batch size."""
+    docs = [
+        Document(
+            page_content="This is a test document.",
+            metadata={"source": "1"},
+        ),
+    ]
+    ids = [_HashedDocument.from_document(doc).uid for doc in docs]
+
+    batch_size = 1
+    with patch.object(vector_store, "add_documents") as mock_add_documents:
+        index(docs, record_manager, vector_store, batch_size=batch_size)
+        args, kwargs = mock_add_documents.call_args
+        assert args == (docs,)
+        assert kwargs == {"ids": ids, "batch_size": batch_size}
+
+
+@pytest.mark.requires("aiosqlite")
+async def test_aindexing_custom_batch_size(
+    arecord_manager: SQLRecordManager, vector_store: InMemoryVectorStore
+) -> None:
+    """Test indexing with a custom batch size."""
+    docs = [
+        Document(
+            page_content="This is a test document.",
+            metadata={"source": "1"},
+        ),
+    ]
+    ids = [_HashedDocument.from_document(doc).uid for doc in docs]
+
+    batch_size = 1
+    with patch.object(vector_store, "aadd_documents") as mock_add_documents:
+        await aindex(docs, arecord_manager, vector_store, batch_size=batch_size)
+        args, kwargs = mock_add_documents.call_args
+        assert args == (docs,)
+        assert kwargs == {"ids": ids, "batch_size": batch_size}