Why aiomysql locks the table even when using context manager? - aiohttp

Question

I noticed that even I execute sql statements inside "with" context manager, after the request is finished, the table queried still locked and I can't execute "truncate" on it until I stop the event loop.
Here is example of my code:
import logging
import asyncio
import aiomysql
from aiohttp import web
from aiomysql.cursors import DictCursor
logging.basicConfig(level=logging.DEBUG)
async def index(request):
async with request.app["mysql"].acquire() as conn:
async with conn.cursor() as cur:
await cur.execute("SELECT * FROM my_table")
lines = await cur.fetchall()
return web.Response(text='Hello Aiohttp!')
async def get_mysql_pool(loop):
pool = await aiomysql.create_pool(
host="localhost",
user="test",
password="test",
db="test",
cursorclass=DictCursor,
loop=loop
)
return pool
if __name__ == "__main__":
loop = asyncio.get_event_loop()
mysql = loop.run_until_complete(get_mysql_pool(loop))
app = web.Application(loop=loop, debug=True)
app["mysql"] = mysql
app.router.add_get("/", index)
web.run_app(app)
After executing curl 'http://localhost:8080/', I'm connecting to mysql server with mysql cli and try to execute "truncate my_table" - it won't finish until I stop aiohttp. How to change this behavior?

Answer 1

Locks held because connection is not in autocommit mode by default. Adding autocommit=True should solve the issue.
pool = await aiomysql.create_pool(
host="localhost",
user="test",
password="test",
db="test",
autocommit=True,
cursorclass=DictCursor,
loop=loop)
Alternatively it is possible to release transaction by explicit command:
await cur.execute("COMMIT;")
Primary purpose of context managers here is to close cursor, not to commit transaction.
aiomysql has SQLAlchemy.core extension with context manager support for transactions, see example here:
https://github.com/aio-libs/aiomysql/blob/93aa3e5f77d77ad5592c3e9519cfc9f9587bf9ac/tests/pep492/test_async_with.py#L214-L234