Add SqliteSaver

langgraph/checkpoint/sqlite.py

@@ -0,0 +1,82 @@
+import pickle
+import sqlite3
+from contextlib import contextmanager
+from typing import Optional
+
+from langchain_core.pydantic_v1 import Field
+from langchain_core.runnables import RunnableConfig
+from langchain_core.runnables.utils import ConfigurableFieldSpec
+
+from langgraph.checkpoint.base import BaseCheckpointSaver, Checkpoint
+
+
+class SqliteSaver(BaseCheckpointSaver):
+    conn: sqlite3.Connection
+
+    is_setup: bool = Field(False, init=False, repr=False)
+
+    class Config:
+        arbitrary_types_allowed = True
+
+    @classmethod
+    def from_conn_string(cls, conn_string: str) -> "SqliteSaver":
+        return SqliteSaver(conn=sqlite3.connect(conn_string))
+
+    @property
+    def config_specs(self) -> list[ConfigurableFieldSpec]:
+        return [
+            ConfigurableFieldSpec(
+                id="thread_id",
+                annotation=str,
+                name="Thread ID",
+                description=None,
+                default="",
+                is_shared=True,
+            ),
+        ]
+
+    def setup(self) -> None:
+        print("Setting up", self.is_setup)
+        if self.is_setup:
+            return
+
+        self.conn.executescript(
+            """
+            CREATE TABLE IF NOT EXISTS checkpoints (
+                thread_id TEXT PRIMARY KEY,
+                checkpoint BLOB
+            );
+            """
+        )
+
+        self.is_setup = True
+
+    @contextmanager
+    def cursor(self, transaction: bool = True):
+        self.setup()
+        cur = self.conn.cursor()
+        try:
+            yield cur
+        finally:
+            if transaction:
+                self.conn.commit()
+            cur.close()
+
+    def get(self, config: RunnableConfig) -> Optional[Checkpoint]:
+        with self.cursor(transaction=False) as cur:
+            cur.execute(
+                "SELECT checkpoint FROM checkpoints WHERE thread_id = ?",
+                (config["configurable"]["thread_id"],),
+            )
+            if value := cur.fetchone():
+                return pickle.loads(value[0])
+
+    def put(self, config: RunnableConfig, checkpoint: Checkpoint) -> None:
+        with self.cursor() as cur:
+            cur.execute(
+                "INSERT OR REPLACE INTO checkpoints (thread_id, checkpoint) VALUES (?, ?)",
+                (
+                    config["configurable"]["thread_id"],
+                    pickle.dumps(checkpoint),
+                ),
+            )