import json import logging from abc import ABC, abstractmethod from typing import Any, List, Optional from sqlalchemy import Column, Integer, Text, create_engine try: from sqlalchemy.orm import declarative_base except ImportError: from sqlalchemy.ext.declarative import declarative_base from langchain_core.chat_history import BaseChatMessageHistory from langchain_core.messages import ( BaseMessage, message_to_dict, messages_from_dict, ) from sqlalchemy.orm import sessionmaker logger = logging.getLogger(__name__) class BaseMessageConverter(ABC): """The class responsible for converting BaseMessage to your SQLAlchemy model.""" @abstractmethod def from_sql_model(self, sql_message: Any) -> BaseMessage: """Convert a SQLAlchemy model to a BaseMessage instance.""" raise NotImplementedError @abstractmethod def to_sql_model(self, message: BaseMessage, session_id: str) -> Any: """Convert a BaseMessage instance to a SQLAlchemy model.""" raise NotImplementedError @abstractmethod def get_sql_model_class(self) -> Any: """Get the SQLAlchemy model class.""" raise NotImplementedError def create_message_model(table_name, DynamicBase): # type: ignore """ Create a message model for a given table name. Args: table_name: The name of the table to use. DynamicBase: The base class to use for the model. Returns: The model class. """ # Model decleared inside a function to have a dynamic table name class Message(DynamicBase): __tablename__ = table_name id = Column(Integer, primary_key=True) session_id = Column(Text) message = Column(Text) return Message class DefaultMessageConverter(BaseMessageConverter): """The default message converter for SQLChatMessageHistory.""" def __init__(self, table_name: str): self.model_class = create_message_model(table_name, declarative_base()) def from_sql_model(self, sql_message: Any) -> BaseMessage: return messages_from_dict([json.loads(sql_message.message)])[0] def to_sql_model(self, message: BaseMessage, session_id: str) -> Any: return self.model_class( session_id=session_id, message=json.dumps(message_to_dict(message)) ) def get_sql_model_class(self) -> Any: return self.model_class class SQLChatMessageHistory(BaseChatMessageHistory): """Chat message history stored in an SQL database.""" def __init__( self, session_id: str, connection_string: str, table_name: str = "message_store", session_id_field_name: str = "session_id", custom_message_converter: Optional[BaseMessageConverter] = None, ): self.connection_string = connection_string self.engine = create_engine(connection_string, echo=False) self.session_id_field_name = session_id_field_name self.converter = custom_message_converter or DefaultMessageConverter(table_name) self.sql_model_class = self.converter.get_sql_model_class() if not hasattr(self.sql_model_class, session_id_field_name): raise ValueError("SQL model class must have session_id column") self._create_table_if_not_exists() self.session_id = session_id self.Session = sessionmaker(self.engine) def _create_table_if_not_exists(self) -> None: self.sql_model_class.metadata.create_all(self.engine) @property def messages(self) -> List[BaseMessage]: # type: ignore """Retrieve all messages from db""" with self.Session() as session: result = ( session.query(self.sql_model_class) .where( getattr(self.sql_model_class, self.session_id_field_name) == self.session_id ) .order_by(self.sql_model_class.id.asc()) ) messages = [] for record in result: messages.append(self.converter.from_sql_model(record)) return messages def add_message(self, message: BaseMessage) -> None: """Append the message to the record in db""" with self.Session() as session: session.add(self.converter.to_sql_model(message, self.session_id)) session.commit() def clear(self) -> None: """Clear session memory from db""" with self.Session() as session: session.query(self.sql_model_class).filter( getattr(self.sql_model_class, self.session_id_field_name) == self.session_id ).delete() session.commit()