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SQL Chat Message History

This notebook goes over a SQLChatMessageHistory class that allows to store chat history in any database supported by SQLAlchemy.

Please note that to use it with databases other than SQLite, you will need to install the corresponding database driver.

Basic Usage​

To use the storage you need to provide only 2 things:

  1. Session Id - a unique identifier of the session, like user name, email, chat id etc.
  2. Connection string - a string that specifies the database connection. It will be passed to SQLAlchemy create_engine function.
from langchain.memory.chat_message_histories import SQLChatMessageHistory

chat_message_history = SQLChatMessageHistory(
    session_id='test_session',
    connection_string='sqlite:///sqlite.db'
)

chat_message_history.add_user_message('Hello')
chat_message_history.add_ai_message('Hi')

API Reference:

chat_message_history.messages
    [HumanMessage(content='Hello', additional_kwargs={}, example=False),
     AIMessage(content='Hi', additional_kwargs={}, example=False)]

Custom Storage Format​

By default, only the session id and message dictionary are stored in the table.

However, sometimes you might want to store some additional information, like message date, author, language etc.

To do that, you can create a custom message converter, by implementing BaseMessageConverter interface.

from datetime import datetime
from langchain.schema import BaseMessage, HumanMessage, AIMessage, SystemMessage
from typing import Any
from sqlalchemy import Column, Integer, Text, DateTime
from sqlalchemy.orm import declarative_base
from langchain.memory.chat_message_histories.sql import BaseMessageConverter


Base = declarative_base()


class CustomMessage(Base):
    __tablename__ = 'custom_message_store'

    id = Column(Integer, primary_key=True)
    session_id = Column(Text)
    type = Column(Text)
    content = Column(Text)
    created_at = Column(DateTime)
    author_email = Column(Text)


class CustomMessageConverter(BaseMessageConverter):
    def __init__(self, author_email: str):
        self.author_email = author_email
    
    def from_sql_model(self, sql_message: Any) -> BaseMessage:
        if sql_message.type == 'human':
            return HumanMessage(
                content=sql_message.content,
            )
        elif sql_message.type == 'ai':
            return AIMessage(
                content=sql_message.content,
            )
        elif sql_message.type == 'system':
            return SystemMessage(
                content=sql_message.content,
            )
        else:
            raise ValueError(f'Unknown message type: {sql_message.type}')
    
    def to_sql_model(self, message: BaseMessage, session_id: str) -> Any:
        now = datetime.now()
        return CustomMessage(
            session_id=session_id,
            type=message.type,
            content=message.content,
            created_at=now,
            author_email=self.author_email
        )
    
    def get_sql_model_class(self) -> Any:
        return CustomMessage


chat_message_history = SQLChatMessageHistory(
    session_id='test_session',
    connection_string='sqlite:///sqlite.db',
    custom_message_converter=CustomMessageConverter(
        author_email='test@example.com'
    )
)

chat_message_history.add_user_message('Hello')
chat_message_history.add_ai_message('Hi')
chat_message_history.messages
    [HumanMessage(content='Hello', additional_kwargs={}, example=False),
     AIMessage(content='Hi', additional_kwargs={}, example=False)]

You also might want to change the name of session_id column. In this case you'll need to specify session_id_field_name parameter.