community[patch]: restore compatibility with SQLAlchemy 1.x (#22546)

- **Description:** Restores compatibility with SQLAlchemy 1.4.x that was
broken since #18992 and adds a test run for this version on CI (only for
Python 3.11)
- **Issue:** fixes #19681
- **Dependencies:** None
- **Twitter handle:** `@krassowski_m`

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

libs/community/langchain_community/document_loaders/sql_database.py

@@ -1,6 +1,7 @@
 from typing import Any, Callable, Dict, Iterator, List, Optional, Sequence, Union
 
-import sqlalchemy as sa
+from sqlalchemy.engine import RowMapping
+from sqlalchemy.sql.expression import Select
 
 from langchain_community.docstore.document import Document
 from langchain_community.document_loaders.base import BaseLoader
@@ -19,7 +20,7 @@ class SQLDatabaseLoader(BaseLoader):
 
     def __init__(
         self,
-        query: Union[str, sa.Select],
+        query: Union[str, Select],
         db: SQLDatabase,
         *,
         parameters: Optional[Dict[str, Any]] = None,
@@ -106,7 +107,7 @@ class SQLDatabaseLoader(BaseLoader):
 
     @staticmethod
     def page_content_default_mapper(
-        row: sa.RowMapping, column_names: Optional[List[str]] = None
+        row: RowMapping, column_names: Optional[List[str]] = None
     ) -> str:
         """
         A reasonable default function to convert a record into a "page content" string.
@@ -121,7 +122,7 @@ class SQLDatabaseLoader(BaseLoader):
 
     @staticmethod
     def metadata_default_mapper(
-        row: sa.RowMapping, column_names: Optional[List[str]] = None
+        row: RowMapping, column_names: Optional[List[str]] = None
     ) -> Dict[str, Any]:
         """
         A reasonable default function to convert a record into a "metadata" dictionary.

libs/community/langchain_community/indexes/_sql_record_manager.py

@@ -13,6 +13,7 @@ allow it to work with a variety of SQL as a backend.
 * Keys can be listed based on the updated at field.
 * Keys can be deleted.
 """
+
 import contextlib
 import decimal
 import uuid
@@ -29,9 +30,7 @@ from typing import (
 )
 
 from sqlalchemy import (
-    URL,
     Column,
-    Engine,
     Float,
     Index,
     String,
@@ -42,15 +41,21 @@ from sqlalchemy import (
     select,
     text,
 )
+from sqlalchemy.engine import URL, Engine
 from sqlalchemy.ext.asyncio import (
     AsyncEngine,
     AsyncSession,
-    async_sessionmaker,
     create_async_engine,
 )
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.orm import Session, sessionmaker
 
+try:
+    from sqlalchemy.ext.asyncio import async_sessionmaker
+except ImportError:
+    # dummy for sqlalchemy < 2
+    async_sessionmaker = type("async_sessionmaker", (type,), {})  # type: ignore
+
 from langchain_community.indexes.base import RecordManager
 
 Base = declarative_base()

libs/community/langchain_community/vectorstores/pgvector.py

@@ -20,7 +20,7 @@ from typing import (
 import numpy as np
 import sqlalchemy
 from langchain_core._api import deprecated, warn_deprecated
-from sqlalchemy import SQLColumnExpression, delete, func
+from sqlalchemy import delete, func
 from sqlalchemy.dialects.postgresql import JSON, JSONB, UUID
 from sqlalchemy.orm import Session, relationship
 
@@ -29,6 +29,12 @@ try:
 except ImportError:
     from sqlalchemy.ext.declarative import declarative_base
 
+try:
+    from sqlalchemy import SQLColumnExpression
+except ImportError:
+    # for sqlalchemy < 2
+    SQLColumnExpression = Any  # type: ignore
+
 from langchain_core.documents import Document
 from langchain_core.embeddings import Embeddings
 from langchain_core.runnables.config import run_in_executor

libs/community/tests/unit_tests/chat_message_histories/test_sql.py

@@ -4,7 +4,17 @@ from typing import Any, AsyncGenerator, Generator, List, Tuple
 import pytest
 from langchain_core.messages import AIMessage, BaseMessage, HumanMessage
 from sqlalchemy import Column, Integer, Text
-from sqlalchemy.orm import DeclarativeBase
+
+try:
+    from sqlalchemy.orm import DeclarativeBase
+
+    class Base(DeclarativeBase):
+        pass
+except ImportError:
+    # for sqlalchemy < 2
+    from sqlalchemy.ext.declarative import declarative_base
+
+    Base = declarative_base()  # type:ignore
 
 from langchain_community.chat_message_histories import SQLChatMessageHistory
 from langchain_community.chat_message_histories.sql import DefaultMessageConverter
@@ -198,9 +208,6 @@ async def test_async_clear_messages(
 
 
 def test_model_no_session_id_field_error(con_str: str) -> None:
-    class Base(DeclarativeBase):
-        pass
-
     class Model(Base):
         __tablename__ = "test_table"
         id = Column(Integer, primary_key=True)

libs/community/tests/unit_tests/test_sql_database.py

@@ -1,21 +1,25 @@
 # flake8: noqa: E501
 """Test SQL database wrapper."""
+
 import pytest
 import sqlalchemy as sa
+from packaging import version
 from sqlalchemy import (
     Column,
     Integer,
     MetaData,
-    Result,
     String,
     Table,
     Text,
     insert,
     select,
 )
+from sqlalchemy.engine import Engine, Result
 
 from langchain_community.utilities.sql_database import SQLDatabase, truncate_word
 
+is_sqlalchemy_v1 = version.parse(sa.__version__).major == 1
+
 metadata_obj = MetaData()
 
 user = Table(
@@ -35,18 +39,18 @@ company = Table(
 
 
 @pytest.fixture
-def engine() -> sa.Engine:
+def engine() -> Engine:
     return sa.create_engine("sqlite:///:memory:")
 
 
 @pytest.fixture
-def db(engine: sa.Engine) -> SQLDatabase:
+def db(engine: Engine) -> SQLDatabase:
     metadata_obj.create_all(engine)
     return SQLDatabase(engine)
 
 
 @pytest.fixture
-def db_lazy_reflection(engine: sa.Engine) -> SQLDatabase:
+def db_lazy_reflection(engine: Engine) -> SQLDatabase:
     metadata_obj.create_all(engine)
     return SQLDatabase(engine, lazy_table_reflection=True)
 
@@ -230,6 +234,7 @@ def test_sql_database_run_update(db: SQLDatabase) -> None:
     assert output == expected_output
 
 
+@pytest.mark.skipif(is_sqlalchemy_v1, reason="Requires SQLAlchemy 2 or newer")
 def test_sql_database_schema_translate_map() -> None:
     """Verify using statement-specific execution options."""
 

libs/langchain/langchain/indexes/_sql_record_manager.py

@@ -13,6 +13,7 @@ allow it to work with a variety of SQL as a backend.
 * Keys can be listed based on the updated at field.
 * Keys can be deleted.
 """
+
 import contextlib
 import decimal
 import uuid
@@ -20,9 +21,7 @@ from typing import Any, AsyncGenerator, Dict, Generator, List, Optional, Sequenc
 
 from langchain_core.indexing import RecordManager
 from sqlalchemy import (
-    URL,
     Column,
-    Engine,
     Float,
     Index,
     String,
@@ -33,15 +32,21 @@ from sqlalchemy import (
     select,
     text,
 )
+from sqlalchemy.engine import URL, Engine
 from sqlalchemy.ext.asyncio import (
     AsyncEngine,
     AsyncSession,
-    async_sessionmaker,
     create_async_engine,
 )
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.orm import Query, Session, sessionmaker
 
+try:
+    from sqlalchemy.ext.asyncio import async_sessionmaker
+except ImportError:
+    # dummy for sqlalchemy < 2
+    async_sessionmaker = type("async_sessionmaker", (type,), {})  # type: ignore
+
 Base = declarative_base()