Enable write ahead log mode in SqliteSaver and AsyncSqliteSaver.

langgraph/checkpoint/aiosqlite.py

@@ -191,6 +191,7 @@ class AsyncSqliteSaver(BaseCheckpointSaver, AbstractAsyncContextManager):
                 await self.conn
             async with self.conn.executescript(
                 """
+                PRAGMA journal_mode=WAL;
                 CREATE TABLE IF NOT EXISTS checkpoints (
                     thread_id TEXT NOT NULL,
                     thread_ts TEXT NOT NULL,

langgraph/checkpoint/sqlite.py

@@ -159,6 +159,7 @@ class SqliteSaver(BaseCheckpointSaver, AbstractContextManager):
 
         self.conn.executescript(
             """
+            PRAGMA journal_mode=WAL;
             CREATE TABLE IF NOT EXISTS checkpoints (
                 thread_id TEXT NOT NULL,
                 thread_ts TEXT NOT NULL,