`langchain_postgres.chat_message_histories`.PostgresChatMessageHistory¶

class langchain_postgres.chat_message_histories.PostgresChatMessageHistory(table_name: str, session_id: str, /, *, sync_connection: Optional[Connection] = None, async_connection: Optional[AsyncConnection] = None)[source]¶

Client for persisting chat message history in a Postgres database,

This client provides support for both sync and async via psycopg >=3.

The client can create schema in the database and provides methods to add messages, get messages, and clear the chat message history.

The schema has the following columns:

id: A serial primary key.
session_id: The session ID for the chat message history.
message: The JSONB message content.
created_at: The timestamp of when the message was created.

Messages are retrieved for a given session_id and are sorted by the id (which should be increasing monotonically), and correspond to the order in which the messages were added to the history.

The “created_at” column is not returned by the interface, but has been added for the schema so the information is available in the database.

A session_id can be used to separate different chat histories in the same table, the session_id should be provided when initializing the client.

This chat history client takes in a psycopg connection object (either Connection or AsyncConnection) and uses it to interact with the database.

This design allows to reuse the underlying connection object across multiple instantiations of this class, making instantiation fast.

This chat history client is designed for prototyping applications that involve chat and are based on Postgres.

As your application grows, you will likely need to extend the schema to handle more complex queries. For example, a chat application may involve multiple tables like a user table, a table for storing chat sessions / conversations, and this table for storing chat messages for a given session. The application will require access to additional endpoints like deleting messages by user id, listing conversations by user id or ordering them based on last message time, etc.

Feel free to adapt this implementation to suit your application’s needs.

Parameters

session_id (str) – The session ID to use for the chat message history
table_name (str) – The name of the database table to use
sync_connection (Optional[psycopg.Connection]) – An existing psycopg connection instance
async_connection (Optional[psycopg.AsyncConnection]) – An existing psycopg async connection instance

Usage:

Use the create_tables or acreate_tables method to set up the table schema in the database.
Initialize the class with the appropriate session ID, table name, and database connection.
Add messages to the database using add_messages or aadd_messages.
Retrieve messages with get_messages or aget_messages.
Clear the session history with clear or aclear when needed.

Note

At least one of sync_connection or async_connection must be provided.

Examples:

import uuid

from langchain_core.messages import SystemMessage, AIMessage, HumanMessage
from langchain_postgres import PostgresChatMessageHistory
import psycopg

# Establish a synchronous connection to the database
# (or use psycopg.AsyncConnection for async)
sync_connection = psycopg2.connect(conn_info)

# Create the table schema (only needs to be done once)
table_name = "chat_history"
PostgresChatMessageHistory.create_tables(sync_connection, table_name)

session_id = str(uuid.uuid4())

# Initialize the chat history manager
chat_history = PostgresChatMessageHistory(
    table_name,
    session_id,
    sync_connection=sync_connection
)

# Add messages to the chat history
chat_history.add_messages([
    SystemMessage(content="Meow"),
    AIMessage(content="woof"),
    HumanMessage(content="bark"),
])

print(chat_history.messages)

Attributes

messages

The abstraction required a property.

Methods

`__init__`(table_name, session_id, /, *[, ...])	Client for persisting chat message history in a Postgres database,
`aadd_messages`(messages)	Add messages to the chat message history.
`aclear`()	Clear the chat message history for the GIVEN session.
`acreate_tables`(connection, table_name, /)	Create the table schema in the database and create relevant indexes.
`add_ai_message`(message)	Convenience method for adding an AI message string to the store.
`add_message`(message)	Add a Message object to the store.
`add_messages`(messages)	Add messages to the chat message history.
`add_user_message`(message)	Convenience method for adding a human message string to the store.
`adrop_table`(connection, table_name, /)	Delete the table schema in the database.
`aget_messages`()	Retrieve messages from the chat message history.
`clear`()	Clear the chat message history for the GIVEN session.
`create_tables`(connection, table_name, /)	Create the table schema in the database and create relevant indexes.
`drop_table`(connection, table_name, /)	Delete the table schema in the database.
`get_messages`()	Retrieve messages from the chat message history.

__init__(table_name: str, session_id: str, /, *, sync_connection: Optional[Connection] = None, async_connection: Optional[AsyncConnection] = None) → None[source]¶

Client for persisting chat message history in a Postgres database,

This client provides support for both sync and async via psycopg >=3.

The client can create schema in the database and provides methods to add messages, get messages, and clear the chat message history.

The schema has the following columns:

id: A serial primary key.
session_id: The session ID for the chat message history.
message: The JSONB message content.
created_at: The timestamp of when the message was created.