mirror of
https://github.com/hwchase17/langchain
synced 2024-11-18 09:25:54 +00:00
141 lines
4.6 KiB
Python
141 lines
4.6 KiB
Python
import json
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import logging
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from abc import ABC, abstractmethod
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from typing import Any, List, Optional
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from sqlalchemy import Column, Integer, Text, create_engine
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try:
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from sqlalchemy.orm import declarative_base
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except ImportError:
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from sqlalchemy.ext.declarative import declarative_base
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from langchain_core.chat_history import BaseChatMessageHistory
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from langchain_core.messages import (
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BaseMessage,
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message_to_dict,
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messages_from_dict,
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)
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from sqlalchemy.orm import sessionmaker
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logger = logging.getLogger(__name__)
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class BaseMessageConverter(ABC):
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"""Class that converts BaseMessage to the SQLAlchemy model."""
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@abstractmethod
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def from_sql_model(self, sql_message: Any) -> BaseMessage:
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"""Convert a SQLAlchemy model to a BaseMessage instance."""
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raise NotImplementedError
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@abstractmethod
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def to_sql_model(self, message: BaseMessage, session_id: str) -> Any:
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"""Convert a BaseMessage instance to a SQLAlchemy model."""
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raise NotImplementedError
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@abstractmethod
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def get_sql_model_class(self) -> Any:
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"""Get the SQLAlchemy model class."""
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raise NotImplementedError
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def create_message_model(table_name: str, DynamicBase: Any) -> Any:
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"""
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Create a message model for a given table name.
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Args:
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table_name: The name of the table to use.
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DynamicBase: The base class to use for the model.
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Returns:
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The model class.
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"""
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# Model declared inside a function to have a dynamic table name.
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class Message(DynamicBase): # type: ignore[valid-type, misc]
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__tablename__ = table_name
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id = Column(Integer, primary_key=True)
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session_id = Column(Text)
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message = Column(Text)
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return Message
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class DefaultMessageConverter(BaseMessageConverter):
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"""The default message converter for SQLChatMessageHistory."""
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def __init__(self, table_name: str):
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self.model_class = create_message_model(table_name, declarative_base())
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def from_sql_model(self, sql_message: Any) -> BaseMessage:
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return messages_from_dict([json.loads(sql_message.message)])[0]
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def to_sql_model(self, message: BaseMessage, session_id: str) -> Any:
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return self.model_class(
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session_id=session_id, message=json.dumps(message_to_dict(message))
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)
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def get_sql_model_class(self) -> Any:
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return self.model_class
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class SQLChatMessageHistory(BaseChatMessageHistory):
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"""Chat message history stored in an SQL database."""
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def __init__(
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self,
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session_id: str,
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connection_string: str,
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table_name: str = "message_store",
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session_id_field_name: str = "session_id",
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custom_message_converter: Optional[BaseMessageConverter] = None,
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):
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self.connection_string = connection_string
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self.engine = create_engine(connection_string, echo=False)
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self.session_id_field_name = session_id_field_name
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self.converter = custom_message_converter or DefaultMessageConverter(table_name)
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self.sql_model_class = self.converter.get_sql_model_class()
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if not hasattr(self.sql_model_class, session_id_field_name):
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raise ValueError("SQL model class must have session_id column")
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self._create_table_if_not_exists()
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self.session_id = session_id
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self.Session = sessionmaker(self.engine)
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def _create_table_if_not_exists(self) -> None:
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self.sql_model_class.metadata.create_all(self.engine)
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@property
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def messages(self) -> List[BaseMessage]: # type: ignore
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"""Retrieve all messages from db"""
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with self.Session() as session:
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result = (
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session.query(self.sql_model_class)
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.where(
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getattr(self.sql_model_class, self.session_id_field_name)
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== self.session_id
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)
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.order_by(self.sql_model_class.id.asc())
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)
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messages = []
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for record in result:
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messages.append(self.converter.from_sql_model(record))
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return messages
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def add_message(self, message: BaseMessage) -> None:
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"""Append the message to the record in db"""
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with self.Session() as session:
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session.add(self.converter.to_sql_model(message, self.session_id))
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session.commit()
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def clear(self) -> None:
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"""Clear session memory from db"""
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with self.Session() as session:
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session.query(self.sql_model_class).filter(
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getattr(self.sql_model_class, self.session_id_field_name)
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== self.session_id
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).delete()
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session.commit()
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