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Postgres Chat Memory

For longer-term persistence across chat sessions, you can swap out the default in-memory chatHistory for a Postgres Database.


First install the node-postgres package:

npm install @langchain/openai @langchain/community pg


Each chat history session is stored in a Postgres database and requires a session id.

The connection to postgres is handled through a pool. You can either pass an instance of a pool via the pool parameter or pass a pool config via the poolConfig parameter. See pg-node docs on pools for more information. A provided pool takes precedence, thus if both a pool instance and a pool config are passed, only the pool will be used.

import pg from "pg";

import { PostgresChatMessageHistory } from "@langchain/community/stores/message/postgres";
import { ChatOpenAI } from "@langchain/openai";
import { RunnableWithMessageHistory } from "@langchain/core/runnables";
import {
} from "@langchain/core/prompts";
import { StringOutputParser } from "@langchain/core/output_parsers";

const poolConfig = {
host: "",
port: 5432,
user: "myuser",
password: "ChangeMe",
database: "api",

const pool = new pg.Pool(poolConfig);

const model = new ChatOpenAI();

const prompt = ChatPromptTemplate.fromMessages([
"You are a helpful assistant. Answer all questions to the best of your ability.",
new MessagesPlaceholder("chat_history"),
["human", "{input}"],

const chain = prompt.pipe(model).pipe(new StringOutputParser());

const chainWithHistory = new RunnableWithMessageHistory({
runnable: chain,
inputMessagesKey: "input",
historyMessagesKey: "chat_history",
getMessageHistory: async (sessionId) => {
const chatHistory = new PostgresChatMessageHistory({
// Can also pass `poolConfig` to initialize the pool internally,
// but easier to call `.end()` at the end later.
return chatHistory;

const res1 = await chainWithHistory.invoke(
input: "Hi! I'm MJDeligan.",
{ configurable: { sessionId: "langchain-test-session" } }
"Hello MJDeligan! It's nice to meet you. My name is AI. How may I assist you today?"

const res2 = await chainWithHistory.invoke(
{ input: "What did I just say my name was?" },
{ configurable: { sessionId: "langchain-test-session" } }

"You said your name was MJDeligan."

// If you provided a pool config you should close the created pool when you are done
await pool.end();

API Reference:

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