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Vadym BardaandGitHub
d12f5c6d8b
* checkpoint-postgres: allow passing pool * make psycopg_pool a non-dev dependency * code review * lockfile * move methods * relax requirements, remove binary * add binary to dev dependencies * update readme
104 lines
3.1 KiB
Markdown
104 lines
3.1 KiB
Markdown
# LangGraph Checkpoint Postgres
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Implementation of LangGraph CheckpointSaver that uses Postgres.
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## Dependencies
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By default `langgraph-checkpoint-postgres` installs `psycopg` (Psycopg 3) without any extras. However, you can choose a specific installation that best suits your needs [here](https://www.psycopg.org/psycopg3/docs/basic/install.html) (for example, `psycopg[binary]`).
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## Usage
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> [!IMPORTANT]
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> When using Postgres checkpointers for the first time, make sure to call `.setup()` method on them to create required tables. See example below.
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> [!IMPORTANT]
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> When manually creating Postgres connections and passing them to `PostgresSaver` or `AsyncPostgresSaver`, make sure to include `autocommit=True` and `row_factory=dict_row` (`from psycopg.rows import dict_row`). See a full example in this [how-to guide](https://langchain-ai.github.io/langgraph/how-tos/persistence_postgres/).
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```python
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from langgraph.checkpoint.postgres import PostgresSaver
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write_config = {"configurable": {"thread_id": "1", "checkpoint_ns": ""}}
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read_config = {"configurable": {"thread_id": "1"}}
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DB_URI = "postgres://postgres:postgres@localhost:5432/postgres?sslmode=disable"
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with PostgresSaver.from_conn_string(DB_URI) as checkpointer:
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# call .setup() the first time you're using the checkpointer
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checkpointer.setup()
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checkpoint = {
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"v": 1,
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"ts": "2024-07-31T20:14:19.804150+00:00",
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"id": "1ef4f797-8335-6428-8001-8a1503f9b875",
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"channel_values": {
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"my_key": "meow",
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"node": "node"
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},
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"channel_versions": {
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"__start__": 2,
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"my_key": 3,
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"start:node": 3,
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"node": 3
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},
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"versions_seen": {
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"__input__": {},
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"__start__": {
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"__start__": 1
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},
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"node": {
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"start:node": 2
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}
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},
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"pending_sends": [],
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}
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# store checkpoint
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checkpointer.put(write_config, checkpoint, {}, {})
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# load checkpoint
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checkpointer.get(read_config)
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# list checkpoints
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list(checkpointer.list(read_config))
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```
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### Async
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```python
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from langgraph.checkpoint.postgres.aio import AsyncPostgresSaver
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async with AsyncPostgresSaver.from_conn_string(DB_URI) as checkpointer:
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checkpoint = {
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"v": 1,
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"ts": "2024-07-31T20:14:19.804150+00:00",
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"id": "1ef4f797-8335-6428-8001-8a1503f9b875",
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"channel_values": {
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"my_key": "meow",
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"node": "node"
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},
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"channel_versions": {
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"__start__": 2,
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"my_key": 3,
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"start:node": 3,
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"node": 3
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},
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"versions_seen": {
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"__input__": {},
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"__start__": {
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"__start__": 1
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},
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"node": {
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"start:node": 2
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}
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},
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"pending_sends": [],
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}
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# store checkpoint
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await checkpointer.aput(write_config, checkpoint, {}, {})
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# load checkpoint
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await checkpointer.aget(read_config)
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# list checkpoints
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[c async for c in checkpointer.alist(read_config)]
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```
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