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DeltaChannel reconstructs its value by replaying ancestor writes through the reducer. Every saver ordered a checkpoint's writes by (task_id, idx), but live execution applies them in task-path order: apply_writes sorts a super-step's tasks by task_path_str(task.path[:3]) before calling channel.update. task_id is a hash of the path, so the two orders are unrelated, and two or more tasks writing one DeltaChannel in a single super-step replayed in an arbitrary permutation. Reducers are only required to be batching-invariant, not order-invariant, so the permutation changes the value: get_state disagreed with what invoke returned, and continuing the thread persisted the reordered replay as the base for later writes. Replay now orders by (task_path, task_id, idx), following the precedent already set for the Send channel by SELECT_PENDING_SENDS_SQL. InMemorySaver and the postgres savers already persisted task_path and only needed the sort key; sqlite accepted task_path on put_writes and dropped it, so the writes table gains the column, added by setup() to databases created by earlier versions. Writes stored without a task_path sort first within their checkpoint, which is where live execution applies the task-less input writes that carry "". Co-authored-by: ErenAta16 <149434812+ErenAta16@users.noreply.github.com> Co-authored-by: ragnarok268 <58264829+ragnarok268@users.noreply.github.com>
88 lines
2.8 KiB
Python
88 lines
2.8 KiB
Python
import sqlite3
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from pathlib import Path
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import aiosqlite
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import pytest
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from langgraph.checkpoint.base import empty_checkpoint
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from langgraph.checkpoint.sqlite import SqliteSaver
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from langgraph.checkpoint.sqlite.aio import AsyncSqliteSaver
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WRITES_BEFORE_TASK_PATH = """
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CREATE TABLE writes (
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thread_id TEXT NOT NULL,
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checkpoint_ns TEXT NOT NULL DEFAULT '',
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checkpoint_id TEXT NOT NULL,
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task_id TEXT NOT NULL,
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idx INTEGER NOT NULL,
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channel TEXT NOT NULL,
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type TEXT,
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value BLOB,
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PRIMARY KEY (thread_id, checkpoint_ns, checkpoint_id, task_id, idx)
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);
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INSERT INTO writes VALUES ('t', '', 'c', 'old-task', 0, 'ch', 'null', X'');
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"""
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@pytest.fixture
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def legacy_db(tmp_path: Path) -> Path:
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db = tmp_path / "legacy.sqlite"
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with sqlite3.connect(db) as conn:
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conn.executescript(WRITES_BEFORE_TASK_PATH)
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return db
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def test_setup_migrates_legacy_writes_table_repeatably(legacy_db: Path) -> None:
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for _ in range(2):
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with SqliteSaver.from_conn_string(str(legacy_db)) as saver:
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saver.setup()
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rows = saver.conn.execute(
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"SELECT task_id, task_path FROM writes"
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).fetchall()
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assert rows == [("old-task", "")]
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@pytest.mark.parametrize("fresh", [True, False], ids=["fresh", "legacy"])
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def test_put_writes_persists_task_path(
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tmp_path: Path, legacy_db: Path, fresh: bool
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) -> None:
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db = tmp_path / "fresh.sqlite" if fresh else legacy_db
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with SqliteSaver.from_conn_string(str(db)) as saver:
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config = saver.put(
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{"configurable": {"thread_id": "t", "checkpoint_ns": ""}},
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empty_checkpoint(),
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{},
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{},
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)
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saver.put_writes(config, [("ch", "v")], "task-1", "~__pregel_pull, node")
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stored = saver.conn.execute(
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"SELECT task_path FROM writes WHERE task_id = 'task-1'"
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).fetchall()
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assert stored == [("~__pregel_pull, node",)]
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async def test_async_setup_migrates_legacy_writes_table_repeatably(
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legacy_db: Path,
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) -> None:
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for _ in range(2):
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async with AsyncSqliteSaver.from_conn_string(str(legacy_db)) as saver:
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await saver.setup()
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config = await saver.aput(
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{"configurable": {"thread_id": "t", "checkpoint_ns": ""}},
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empty_checkpoint(),
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{},
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{},
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)
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await saver.aput_writes(
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config, [("ch", "v")], "task-1", "~__pregel_pull, node"
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)
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async with aiosqlite.connect(legacy_db) as conn:
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async with conn.execute(
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"SELECT DISTINCT task_id, task_path FROM writes ORDER BY task_id"
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) as cur:
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assert await cur.fetchall() == [
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("old-task", ""),
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("task-1", "~__pregel_pull, node"),
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]
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