DOC: Postgres Schema for LangGraph Checkpointer

[Farhana-Asgar6]

Issue with current documentation:

https://github.com/langchain-ai/langgraph/blob/main/libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py

schema created when using Langgraph Checkpointer with postgres.
setup() function in class AsyncPostgresSaver

Idea or request for content:

I am looking for documentation that explains the schema created when using the LangGraph checkpointer with Postgres. Currently, I have not been able to find any references in the docs. Could you please add or point me to documentation that outlines the tables and schema details?

This would be very helpful for understanding and exploring LangGraph further.

[punith300i]

LangGraph's PostgreSQL checkpointer by default saves the checkpointer tables into the public schema of a PostgreSQL DB. The checkpointer under the hood uses psycopg3 for handling connections to the PostgreSQL DB.

To use a different db schema, we can leverage the psycopg3 db connection options to add a search_path option as mentioned in PostgreSQL search_path docs.

options="-c search_path=<custom schema name>,public"

Example:
we could include a custom schema to checkpointer by adding this options to the DB URI.

postgresql://<user_name>:<pwd>@<host>:<port>/<db_name>?options=-csearch_path%3D<custom schema name>,public

[code2tan]

use AsyncConnectionPool class

    # 创建异步连接池
    async_connection_pool = AsyncConnectionPool[AsyncConnection[dict[str, Any]]](
        conninfo=db.get_db_conn_url(),
        max_size=20,
        kwargs={
            "autocommit": True,
            "prepare_threshold": 0,
            "row_factory": dict_row,
        },
    )

    # 创建异步 PostgreSQL 保存器
    checkpointer = AsyncPostgresSaver(conn=async_connection_pool, serde=JsonOnlySerializer())

get_db_conn_url() return :

postgresql://<user_name>:<pwd>@<host>:<port>/<db_name>?options=-csearch_path%3D<custom schema name>,public

JsonOnlySerializer optional setting， you can use:

checkpointer = AsyncPostgresSaver(conn=async_connection_pool)