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In Memory Store

This example demonstrates how to setup chat history storage using the InMemoryStore KV store integration.

Usage

The InMemoryStore allows for a generic type to be assigned to the values in the store. We'll assign type BaseMessage as the type of our values, keeping with the theme of a chat history store.

import { InMemoryStore } from "@langchain/core/stores";
import { AIMessage, BaseMessage, HumanMessage } from "@langchain/core/messages";

// Instantiate the store using the `fromPath` method.
const store = new InMemoryStore<BaseMessage>();
/**
* Here you would define your LLM and chat chain, call
* the LLM and eventually get a list of messages.
* For this example, we'll assume we already have a list.
*/
const messages = Array.from({ length: 5 }).map((_, index) => {
if (index % 2 === 0) {
return new AIMessage("ai stuff...");
}
return new HumanMessage("human stuff...");
});
// Set your messages in the store
// The key will be prefixed with `message:id:` and end
// with the index.
await store.mset(
messages.map((message, index) => [`message:id:${index}`, message])
);
// Now you can get your messages from the store
const retrievedMessages = await store.mget(["message:id:0", "message:id:1"]);
console.log(retrievedMessages.map((v) => v));
/**
[
AIMessage {
lc_kwargs: { content: 'ai stuff...', additional_kwargs: {} },
content: 'ai stuff...',
...
},
HumanMessage {
lc_kwargs: { content: 'human stuff...', additional_kwargs: {} },
content: 'human stuff...',
...
}
]
*/
// Or, if you want to get back all the keys you can call
// the `yieldKeys` method.
// Optionally, you can pass a key prefix to only get back
// keys which match that prefix.
const yieldedKeys = [];
for await (const key of store.yieldKeys("message:id:")) {
yieldedKeys.push(key);
}
// The keys are not encoded, so no decoding is necessary
console.log(yieldedKeys);
/**
[
'message:id:0',
'message:id:1',
'message:id:2',
'message:id:3',
'message:id:4'
]
*/
// Finally, let's delete the keys from the store
await store.mdelete(yieldedKeys);

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