community[minor]: Add async methods to CassandraLoader (#20609)

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

libs/community/langchain_community/document_loaders/cassandra.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 from typing import (
     TYPE_CHECKING,
     Any,
+    AsyncIterator,
     Callable,
     Iterator,
     Optional,
@@ -13,6 +14,7 @@ from typing import (
 from langchain_core.documents import Document
 
 from langchain_community.document_loaders.base import BaseLoader
+from langchain_community.utilities.cassandra import wrapped_response_future
 
 _NOT_SET = object()
 
@@ -112,3 +114,15 @@ class CassandraLoader(BaseLoader):
             yield Document(
                 page_content=self.page_content_mapper(row), metadata=metadata
             )
+
+    async def alazy_load(self) -> AsyncIterator[Document]:
+        for row in await wrapped_response_future(
+            self.session.execute_async,
+            self.query,
+            **self.query_kwargs,
+        ):
+            metadata = self.metadata.copy()
+            metadata.update(self.metadata_mapper(row))
+            yield Document(
+                page_content=self.page_content_mapper(row), metadata=metadata
+            )

libs/community/langchain_community/utilities/cassandra.py

@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+import asyncio
+from typing import TYPE_CHECKING, Any, Callable
+
+if TYPE_CHECKING:
+    from cassandra.cluster import ResponseFuture
+
+
+async def wrapped_response_future(
+    func: Callable[..., ResponseFuture], *args: Any, **kwargs: Any
+) -> Any:
+    loop = asyncio.get_event_loop()
+    asyncio_future = loop.create_future()
+    response_future = func(*args, **kwargs)
+
+    def success_handler(_: Any) -> None:
+        loop.call_soon_threadsafe(asyncio_future.set_result, response_future.result())
+
+    def error_handler(exc: BaseException) -> None:
+        loop.call_soon_threadsafe(asyncio_future.set_exception, exc)
+
+    response_future.add_callbacks(success_handler, error_handler)
+    return await asyncio_future

libs/community/tests/integration_tests/document_loaders/test_cassandra.py

@@ -55,9 +55,9 @@ def keyspace() -> Iterator[str]:
     session.execute(f"DROP TABLE IF EXISTS {keyspace}.{CASSANDRA_TABLE}")
 
 
-def test_loader_table(keyspace: str) -> None:
+async def test_loader_table(keyspace: str) -> None:
     loader = CassandraLoader(table=CASSANDRA_TABLE)
-    assert loader.load() == [
+    expected = [
         Document(
             page_content="Row(row_id='id1', body_blob='text1')",
             metadata={"table": CASSANDRA_TABLE, "keyspace": keyspace},
@@ -67,24 +67,28 @@ def test_loader_table(keyspace: str) -> None:
             metadata={"table": CASSANDRA_TABLE, "keyspace": keyspace},
         ),
     ]
+    assert loader.load() == expected
+    assert await loader.aload() == expected
 
 
-def test_loader_query(keyspace: str) -> None:
+async def test_loader_query(keyspace: str) -> None:
     loader = CassandraLoader(
         query=f"SELECT body_blob FROM {keyspace}.{CASSANDRA_TABLE}"
     )
-    assert loader.load() == [
+    expected = [
         Document(page_content="Row(body_blob='text1')"),
         Document(page_content="Row(body_blob='text2')"),
     ]
+    assert loader.load() == expected
+    assert await loader.aload() == expected
 
 
-def test_loader_page_content_mapper(keyspace: str) -> None:
+async def test_loader_page_content_mapper(keyspace: str) -> None:
     def mapper(row: Any) -> str:
         return str(row.body_blob)
 
     loader = CassandraLoader(table=CASSANDRA_TABLE, page_content_mapper=mapper)
-    assert loader.load() == [
+    expected = [
         Document(
             page_content="text1",
             metadata={"table": CASSANDRA_TABLE, "keyspace": keyspace},
@@ -94,14 +98,16 @@ def test_loader_page_content_mapper(keyspace: str) -> None:
             metadata={"table": CASSANDRA_TABLE, "keyspace": keyspace},
         ),
     ]
+    assert loader.load() == expected
+    assert await loader.aload() == expected
 
 
-def test_loader_metadata_mapper(keyspace: str) -> None:
+async def test_loader_metadata_mapper(keyspace: str) -> None:
     def mapper(row: Any) -> dict:
         return {"id": row.row_id}
 
     loader = CassandraLoader(table=CASSANDRA_TABLE, metadata_mapper=mapper)
-    assert loader.load() == [
+    expected = [
         Document(
             page_content="Row(row_id='id1', body_blob='text1')",
             metadata={
@@ -119,3 +125,5 @@ def test_loader_metadata_mapper(keyspace: str) -> None:
             },
         ),
     ]
+    assert loader.load() == expected
+    assert await loader.aload() == expected