langgraph/libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py

import asyncio
from contextlib import asynccontextmanager
from typing import Any, AsyncIterator, Iterator, Optional, Sequence, Union

from langchain_core.runnables import RunnableConfig
from psycopg import AsyncConnection, AsyncCursor, AsyncPipeline
from psycopg.errors import UndefinedTable
from psycopg.rows import DictRow, dict_row
from psycopg.types.json import Jsonb
from psycopg_pool import AsyncConnectionPool

from langgraph.checkpoint.base import (
    WRITES_IDX_MAP,
    ChannelVersions,
    Checkpoint,
    CheckpointMetadata,
    CheckpointTuple,
    get_checkpoint_id,
)
from langgraph.checkpoint.postgres.base import BasePostgresSaver
from langgraph.checkpoint.serde.base import SerializerProtocol

Conn = Union[AsyncConnection[DictRow], AsyncConnectionPool[AsyncConnection[DictRow]]]


@asynccontextmanager
async def _get_connection(
    conn: Conn,
) -> AsyncIterator[AsyncConnection[DictRow]]:
    if isinstance(conn, AsyncConnection):
        yield conn
    elif isinstance(conn, AsyncConnectionPool):
        async with conn.connection() as conn:
            yield conn
    else:
        raise TypeError(f"Invalid connection type: {type(conn)}")


class AsyncPostgresSaver(BasePostgresSaver):
    lock: asyncio.Lock

    def __init__(
        self,
        conn: Conn,
        pipe: Optional[AsyncPipeline] = None,
        serde: Optional[SerializerProtocol] = None,
    ) -> None:
        super().__init__(serde=serde)
        if isinstance(conn, AsyncConnectionPool) and pipe is not None:
            raise ValueError(
                "Pipeline should be used only with a single AsyncConnection, not AsyncConnectionPool."
            )

        self.conn = conn
        self.pipe = pipe
        self.lock = asyncio.Lock()
        self.loop = asyncio.get_running_loop()

    @classmethod
    @asynccontextmanager
    async def from_conn_string(
        cls,
        conn_string: str,
        *,
        pipeline: bool = False,
        serde: Optional[SerializerProtocol] = None,
    ) -> AsyncIterator["AsyncPostgresSaver"]:
        """Create a new PostgresSaver instance from a connection string.

        Args:
            conn_string (str): The Postgres connection info string.
            pipeline (bool): whether to use AsyncPipeline

        Returns:
            AsyncPostgresSaver: A new AsyncPostgresSaver instance.
        """
        async with await AsyncConnection.connect(
            conn_string, autocommit=True, prepare_threshold=0, row_factory=dict_row
        ) as conn:
            if pipeline:
                async with conn.pipeline() as pipe:
                    yield AsyncPostgresSaver(conn=conn, pipe=pipe, serde=serde)
            else:
                yield AsyncPostgresSaver(conn=conn, serde=serde)

    async def setup(self) -> None:
        """Set up the checkpoint database asynchronously.

        This method creates the necessary tables in the Postgres database if they don't
        already exist and runs database migrations. It MUST be called directly by the user
        the first time checkpointer is used.
        """
        async with self._cursor() as cur:
            try:
                results = await cur.execute(
                    "SELECT v FROM checkpoint_migrations ORDER BY v DESC LIMIT 1"
                )
                row = await results.fetchone()
                if row is None:
                    version = -1
                else:
                    version = row["v"]
            except UndefinedTable:
                version = -1
            for v, migration in zip(
                range(version + 1, len(self.MIGRATIONS)),
                self.MIGRATIONS[version + 1 :],
            ):
                await cur.execute(migration)
                await cur.execute(f"INSERT INTO checkpoint_migrations (v) VALUES ({v})")
        if self.pipe:
            await self.pipe.sync()

    async def alist(
        self,
        config: Optional[RunnableConfig],
        *,
        filter: Optional[dict[str, Any]] = None,
        before: Optional[RunnableConfig] = None,
        limit: Optional[int] = None,
    ) -> AsyncIterator[CheckpointTuple]:
        """List checkpoints from the database asynchronously.

        This method retrieves a list of checkpoint tuples from the Postgres database based
        on the provided config. The checkpoints are ordered by checkpoint ID in descending order (newest first).

        Args:
            config (Optional[RunnableConfig]): Base configuration for filtering checkpoints.
            filter (Optional[Dict[str, Any]]): Additional filtering criteria for metadata.
            before (Optional[RunnableConfig]): If provided, only checkpoints before the specified checkpoint ID are returned. Defaults to None.
            limit (Optional[int]): Maximum number of checkpoints to return.

        Yields:
            AsyncIterator[CheckpointTuple]: An asynchronous iterator of matching checkpoint tuples.
        """
        where, args = self._search_where(config, filter, before)
        query = self.SELECT_SQL + where + " ORDER BY checkpoint_id DESC"
        if limit:
            query += f" LIMIT {limit}"
        # if we change this to use .stream() we need to make sure to close the cursor
        async with self._cursor() as cur:
            await cur.execute(query, args, binary=True)
            async for value in cur:
                yield CheckpointTuple(
                    {
                        "configurable": {
                            "thread_id": value["thread_id"],
                            "checkpoint_ns": value["checkpoint_ns"],
                            "checkpoint_id": value["checkpoint_id"],
                        }
                    },
                    await asyncio.to_thread(
                        self._load_checkpoint,
                        value["checkpoint"],
                        value["channel_values"],
                        value["pending_sends"],
                    ),
                    self._load_metadata(value["metadata"]),
                    {
                        "configurable": {
                            "thread_id": value["thread_id"],
                            "checkpoint_ns": value["checkpoint_ns"],
                            "checkpoint_id": value["parent_checkpoint_id"],
                        }
                    }
                    if value["parent_checkpoint_id"]
                    else None,
                    await asyncio.to_thread(self._load_writes, value["pending_writes"]),
                )

    async def aget_tuple(self, config: RunnableConfig) -> Optional[CheckpointTuple]:
        """Get a checkpoint tuple from the database asynchronously.

        This method retrieves a checkpoint tuple from the Postgres database based on the
        provided config. If the config contains a "checkpoint_id" key, the checkpoint with
        the matching thread ID and "checkpoint_id" is retrieved. Otherwise, the latest checkpoint
        for the given thread ID is retrieved.

        Args:
            config (RunnableConfig): The config to use for retrieving the checkpoint.

        Returns:
            Optional[CheckpointTuple]: The retrieved checkpoint tuple, or None if no matching checkpoint was found.
        """
        thread_id = config["configurable"]["thread_id"]
        checkpoint_id = get_checkpoint_id(config)
        checkpoint_ns = config["configurable"].get("checkpoint_ns", "")
        if checkpoint_id:
            args: tuple[Any, ...] = (thread_id, checkpoint_ns, checkpoint_id)
            where = "WHERE thread_id = %s AND checkpoint_ns = %s AND checkpoint_id = %s"
        else:
            args = (thread_id, checkpoint_ns)
            where = "WHERE thread_id = %s AND checkpoint_ns = %s ORDER BY checkpoint_id DESC LIMIT 1"

        async with self._cursor() as cur:
            await cur.execute(
                self.SELECT_SQL + where,
                args,
                binary=True,
            )

            async for value in cur:
                return CheckpointTuple(
                    {
                        "configurable": {
                            "thread_id": thread_id,
                            "checkpoint_ns": checkpoint_ns,
                            "checkpoint_id": value["checkpoint_id"],
                        }
                    },
                    await asyncio.to_thread(
                        self._load_checkpoint,
                        value["checkpoint"],
                        value["channel_values"],
                        value["pending_sends"],
                    ),
                    self._load_metadata(value["metadata"]),
                    {
                        "configurable": {
                            "thread_id": thread_id,
                            "checkpoint_ns": checkpoint_ns,
                            "checkpoint_id": value["parent_checkpoint_id"],
                        }
                    }
                    if value["parent_checkpoint_id"]
                    else None,
                    await asyncio.to_thread(self._load_writes, value["pending_writes"]),
                )

    async def aput(
        self,
        config: RunnableConfig,
        checkpoint: Checkpoint,
        metadata: CheckpointMetadata,
        new_versions: ChannelVersions,
    ) -> RunnableConfig:
        """Save a checkpoint to the database asynchronously.

        This method saves a checkpoint to the Postgres database. The checkpoint is associated
        with the provided config and its parent config (if any).

        Args:
            config (RunnableConfig): The config to associate with the checkpoint.
            checkpoint (Checkpoint): The checkpoint to save.
            metadata (CheckpointMetadata): Additional metadata to save with the checkpoint.
            new_versions (ChannelVersions): New channel versions as of this write.

        Returns:
            RunnableConfig: Updated configuration after storing the checkpoint.
        """
        configurable = config["configurable"].copy()
        thread_id = configurable.pop("thread_id")
        checkpoint_ns = configurable.pop("checkpoint_ns")
        checkpoint_id = configurable.pop(
            "checkpoint_id", configurable.pop("thread_ts", None)
        )

        copy = checkpoint.copy()
        next_config = {
            "configurable": {
                "thread_id": thread_id,
                "checkpoint_ns": checkpoint_ns,
                "checkpoint_id": checkpoint["id"],
            }
        }

        async with self._cursor(pipeline=True) as cur:
            await cur.executemany(
                self.UPSERT_CHECKPOINT_BLOBS_SQL,
                await asyncio.to_thread(
                    self._dump_blobs,
                    thread_id,
                    checkpoint_ns,
                    copy.pop("channel_values"),  # type: ignore[misc]
                    new_versions,
                ),
            )
            await cur.execute(
                self.UPSERT_CHECKPOINTS_SQL,
                (
                    thread_id,
                    checkpoint_ns,
                    checkpoint["id"],
                    checkpoint_id,
                    Jsonb(self._dump_checkpoint(copy)),
                    self._dump_metadata(metadata),
                ),
            )
        return next_config

    async def aput_writes(
        self,
        config: RunnableConfig,
        writes: Sequence[tuple[str, Any]],
        task_id: str,
    ) -> None:
        """Store intermediate writes linked to a checkpoint asynchronously.

        This method saves intermediate writes associated with a checkpoint to the database.

        Args:
            config (RunnableConfig): Configuration of the related checkpoint.
            writes (Sequence[Tuple[str, Any]]): List of writes to store, each as (channel, value) pair.
            task_id (str): Identifier for the task creating the writes.
        """
        query = (
            self.UPSERT_CHECKPOINT_WRITES_SQL
            if all(w[0] in WRITES_IDX_MAP for w in writes)
            else self.INSERT_CHECKPOINT_WRITES_SQL
        )
        params = await asyncio.to_thread(
            self._dump_writes,
            config["configurable"]["thread_id"],
            config["configurable"]["checkpoint_ns"],
            config["configurable"]["checkpoint_id"],
            task_id,
            writes,
        )
        async with self._cursor(pipeline=True) as cur:
            await cur.executemany(query, params)

    @asynccontextmanager
    async def _cursor(
        self, *, pipeline: bool = False
    ) -> AsyncIterator[AsyncCursor[DictRow]]:
        async with _get_connection(self.conn) as conn:
            if self.pipe:
                # a connection in pipeline mode can be used concurrently
                # in multiple threads/coroutines, but only one cursor can be
                # used at a time
                try:
                    async with conn.cursor(binary=True, row_factory=dict_row) as cur:
                        yield cur
                finally:
                    if pipeline:
                        await self.pipe.sync()
            elif pipeline:
                # a connection not in pipeline mode can only be used by one
                # thread/coroutine at a time, so we acquire a lock
                async with self.lock, conn.pipeline(), conn.cursor(
                    binary=True, row_factory=dict_row
                ) as cur:
                    yield cur
            else:
                async with self.lock, conn.cursor(
                    binary=True, row_factory=dict_row
                ) as cur:
                    yield cur

    def list(
        self,
        config: Optional[RunnableConfig],
        *,
        filter: Optional[dict[str, Any]] = None,
        before: Optional[RunnableConfig] = None,
        limit: Optional[int] = None,
    ) -> Iterator[CheckpointTuple]:
        """List checkpoints from the database.

        This method retrieves a list of checkpoint tuples from the Postgres database based
        on the provided config. The checkpoints are ordered by checkpoint ID in descending order (newest first).

        Args:
            config (Optional[RunnableConfig]): Base configuration for filtering checkpoints.
            filter (Optional[Dict[str, Any]]): Additional filtering criteria for metadata.
            before (Optional[RunnableConfig]): If provided, only checkpoints before the specified checkpoint ID are returned. Defaults to None.
            limit (Optional[int]): Maximum number of checkpoints to return.

        Yields:
            Iterator[CheckpointTuple]: An iterator of matching checkpoint tuples.
        """
        aiter_ = self.alist(config, filter=filter, before=before, limit=limit)
        while True:
            try:
                yield asyncio.run_coroutine_threadsafe(
                    anext(aiter_),
                    self.loop,
                ).result()
            except StopAsyncIteration:
                break

    def get_tuple(self, config: RunnableConfig) -> Optional[CheckpointTuple]:
        """Get a checkpoint tuple from the database.

        This method retrieves a checkpoint tuple from the Postgres database based on the
        provided config. If the config contains a "checkpoint_id" key, the checkpoint with
        the matching thread ID and "checkpoint_id" is retrieved. Otherwise, the latest checkpoint
        for the given thread ID is retrieved.

        Args:
            config (RunnableConfig): The config to use for retrieving the checkpoint.

        Returns:
            Optional[CheckpointTuple]: The retrieved checkpoint tuple, or None if no matching checkpoint was found.
        """
        try:
            # check if we are in the main thread, only bg threads can block
            # we don't check in other methods to avoid the overhead
            if asyncio.get_running_loop() is self.loop:
                raise asyncio.InvalidStateError(
                    "Synchronous calls to AsyncPostgresSaver are only allowed from a "
                    "different thread. From the main thread, use the async interface."
                    "For example, use `await checkpointer.aget_tuple(...)` or `await "
                    "graph.ainvoke(...)`."
                )
        except RuntimeError:
            pass
        return asyncio.run_coroutine_threadsafe(
            self.aget_tuple(config), self.loop
        ).result()

    def put(
        self,
        config: RunnableConfig,
        checkpoint: Checkpoint,
        metadata: CheckpointMetadata,
        new_versions: ChannelVersions,
    ) -> RunnableConfig:
        """Save a checkpoint to the database.

        This method saves a checkpoint to the Postgres database. The checkpoint is associated
        with the provided config and its parent config (if any).

        Args:
            config (RunnableConfig): The config to associate with the checkpoint.
            checkpoint (Checkpoint): The checkpoint to save.
            metadata (CheckpointMetadata): Additional metadata to save with the checkpoint.
            new_versions (ChannelVersions): New channel versions as of this write.

        Returns:
            RunnableConfig: Updated configuration after storing the checkpoint.
        """
        return asyncio.run_coroutine_threadsafe(
            self.aput(config, checkpoint, metadata, new_versions), self.loop
        ).result()

    def put_writes(
        self,
        config: RunnableConfig,
        writes: Sequence[tuple[str, Any]],
        task_id: str,
    ) -> None:
        """Store intermediate writes linked to a checkpoint.

        This method saves intermediate writes associated with a checkpoint to the database.

        Args:
            config (RunnableConfig): Configuration of the related checkpoint.
            writes (Sequence[Tuple[str, Any]]): List of writes to store, each as (channel, value) pair.
            task_id (str): Identifier for the task creating the writes.
        """
        return asyncio.run_coroutine_threadsafe(
            self.aput_writes(config, writes, task_id), self.loop
        ).result()