Hi, I am writing some unit tests, and I am getting blocked waiting for a
metadata lock (in MySQL) due to an open connection.
The code is roughly:
metadata.drop_all(engine)
metadata.create_all(engine)
conn = engine.connect()
sql = sa.text('select * from table')
rows = conn.execute(sql).fetchall()
print(conn.closed) # False
print(conn.in_transaction()) # False
# conn.close() # This seems to be required!
metadata.drop_all(engine) # is blocked
metadata.create_all(engine)
A single table is sufficient. So basically: drop, create, select, drop,
create. The hang happens at the second "drop".
This seems to be related to autocommit
(https://docs.sqlalchemy.org/en/latest/core/connections.html#understanding-autocommit)
and if I'm understanding it correctly, the issue is that there must still
be a transaction open. Had I done DML instead of a SELECT, SQLAlchemy would
have autocommitted for me and there would have been no block. Had I
executed with `execution_options(autocommit=True)`, then there would have
been no block. Had I used a transaction via `with conn.begin()`, then
similarly, there would have been no block. Had I also executed:
`conn.execute(sa.text('COMMIT'))` then the transaction would have been
closed and there would have been no block.
Assuming the above is correct, why is it that `conn.in_transaction()` does
not indicate that a transaction is in progress?
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