Langgraph state reset

[Bennoo]

Hey there,
Looking for a way to reset (delete) the state of a graph.

I am using SqliteSaver, in memory, and at some time I would like to be able to reset to empty the state of a graph.
I don't find an easy way to do it..

Thanks

[vbarda]

Hi @Bennoo . There are a few things you can do:

(1) you can just start a new thread -- it will have a new empty state
(2) for in-memory you can just re-instantiate the saver or for SQLite you can delete the underlying file
(3) you can subclass either of existing checkpointers and add a method to clear if absolutely necessary

Hope this helps!

[Bennoo]

Thank you!
I would like to reset the state without changing thread id.
I already have a graph compiled and I don't want to recompile it.

I tried this:

config={"configurable": {"thread_id": thread_id}}
memory = AsyncSqliteSaver.from_conn_string(":memory:")
checkpoint = empty_checkpoint()
await memory.aput(config=config, checkpoint=checkpoint, metadata={})

It seems it is not working, the state is still there with all the variables set, when I get the state with

graph.aget_state(config)

I still see all the properties of the state, I expected to see them empty.
I know I probably do something wrong here but I just don't get the way to update (reset) the state from outside of the execution of the graph.

Thanks

[vbarda]

you shouldn't manually be calling memory.put() -- checkpointing should be handled by langgraph only. if it's hard requirement to clear the thread, you can implement some helpers to drop all records for the thread ID from checkpoints and writes tables in your sqlite database

[Bennoo]

thank you, could you please point me resources where I can find examples or guidance to drop records from checkpoints?
My use case is a chat bot with a langgraph backend. The threadId is linked to the user and I would like to give the possibility to wipe everything and start from scratch. But I cannot changed the threadId and I don't want the memory to go wild by multiplicating the threads.

[vbarda]

unfortunately we don't have any resources / examples for that as it's not something we generally recommend. here is the implementation for the sqlite checkpointer with all the relevant tables / queries, so to implement that you would just need to write DELETE FROM sql queries

[vbarda]

by the way, for your use case, i would not recommend linking thread ID to the user ID (i might have misunderstood you but it almost sounds like you have only one thread per user) -- thread ID is just a chat / session ID, and a single user can have multiple chats potentially

if the intent is starting from scratch, you should just make a new thread

[Bennoo]

but then the old thread is still there right? I mean the data.

[vbarda]

yes, the data for the old thread is still there, so if the concern is removing the old threads, then DELETE FROM approach from the above should help

[Bennoo]

Ok , thanks I don't want the memory to become saturated by old threads that are no more used nor reachable.

[jain009deep]

@Bennoo @vbarda how do you recommend same for memory saver and postgressaver? This seems like a legitimate need else your memory will keep on growing

[Bennoo]

Hello @jain009deep !
I made a simple solution that is making a 'delete' statement in the database.
The structure is simple. There only 2 tables with the thread_id as primary key.
I don't have access to it now but I can share it with you in 2 days if you want.

[theivanfranco]

Hello @Bennoo ! I'd be curious to see your implementation if you are willing to share :) I'm currently facing a similar issue with MemorySaver.

[Bennoo]

I did a really simple piece of code. The data structure is really simple in the database. For PostgreSQL database:

cursor = self.graph.checkpointer.conn.cursor()
# try to delete the thread_id from the checkpoints and writes tables
try:
    cursor.execute("DELETE FROM checkpoints WHERE thread_id = %s", (thread_id,))
    cursor.execute("DELETE FROM checkpoint_writes WHERE thread_id = %s", (thread_id,))
    cursor.execute("DELETE FROM checkpoint_blobs WHERE thread_id = %s", (thread_id,))

    self.graph.checkpointer.conn.commit()
except Exception as exception:
    # Whatever
    pass

For usage with SQLite this is the same but the formatting of the SQL is a bit different:

cursor = self.graph.checkpointer.conn.cursor()
# try to delete the thread_id from the checkpoints and writes tables
try:
    cursor.execute("DELETE FROM checkpoints WHERE thread_id = ?", (thread_id,))
    cursor.execute("DELETE FROM checkpoint_writes WHERE thread_id = ?", (thread_id,))
    cursor.execute("DELETE FROM checkpoint_blobs WHERE thread_id = ?", (thread_id,))

    self.graph.checkpointer.conn.commit()
except Exception as exception:
    # Whatever
    pass

Not tested with SQLite but should work like that.