Better fix for collation error in select query.

Instead of sending a SET NAMES query when creating the connection, do a
conversion of the column value returned from the JSON_TABLE call to the
utf8mb4 character set using its default collation. For some reason, this
is necessary or else that column ends up with a different collation.

langgraph/checkpoint/mysql/aio.py

@@ -6,8 +6,6 @@
 from typing import Any, Optional, cast
 
 import aiomysql  # type: ignore
-import pymysql
-import pymysql.connections
 from langchain_core.runnables import RunnableConfig
 from typing_extensions import Self, override
 
@@ -87,10 +85,6 @@ async def from_conn_string(
             **cls.parse_conn_string(conn_string),
             autocommit=True,
         ) as conn:
-            # This seems necessary until https://github.com/PyMySQL/PyMySQL/pull/1119
-            # is merged into aiomysql.
-            await conn.set_charset(pymysql.connections.DEFAULT_CHARSET)
-
             yield cls(conn=conn, serde=serde)
 
     async def setup(self) -> None:
@@ -494,10 +488,6 @@ async def from_conn_string(
             **AIOMySQLSaver.parse_conn_string(conn_string),
             autocommit=True,
         ) as conn:
-            # This seems necessary until https://github.com/PyMySQL/PyMySQL/pull/1119
-            # is merged into aiomysql.
-            await conn.set_charset(pymysql.connections.DEFAULT_CHARSET)
-
             yield cls(conn=conn, serde=serde)
 
     @override

langgraph/checkpoint/mysql/base.py

@@ -133,7 +133,7 @@
             ) as version
             from json_table(
                 json_keys(checkpoint, '$.channel_versions'),
-                '$[*]' columns (channel VARCHAR(150) PATH '$')
+                '$[*]' columns (channel VARCHAR(150) CHARACTER SET utf8mb4 PATH '$')
             ) as channels
         ) as channel_versions
         inner join checkpoint_blobs bl

langgraph/checkpoint/mysql/shallow.py

@@ -83,7 +83,7 @@
         select json_arrayagg(json_array(bl.channel, bl.type, bl.blob))
         from json_table(
             json_keys(checkpoint, '$.channel_versions'),
-            '$[*]' columns (channel VARCHAR(150) PATH '$')
+            '$[*]' columns (channel VARCHAR(150) CHARACTER SET utf8mb4 PATH '$')
         ) as channels
         inner join checkpoint_blobs bl
             on bl.channel = channels.channel

langgraph/store/mysql/aio.py

@@ -7,7 +7,6 @@
 
 import aiomysql  # type: ignore
 import orjson
-import pymysql
 
 from langgraph.checkpoint.mysql import _ainternal
 from langgraph.store.base import (
@@ -93,10 +92,6 @@ async def from_conn_string(
             **cls.parse_conn_string(conn_string),
             autocommit=True,
         ) as conn:
-            # This seems necessary until https://github.com/PyMySQL/PyMySQL/pull/1119
-            # is merged into aiomysql.
-            await conn.set_charset(pymysql.connections.DEFAULT_CHARSET)
-
             yield cls(conn=conn)
 
     async def setup(self) -> None:

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "langgraph-checkpoint-mysql"
-version = "2.0.10"
+version = "2.0.11"
 description = "Library with a MySQL implementation of LangGraph checkpoint saver."
 authors = ["Theodore Ni <[email protected]>"]
 license = "MIT"