Annotating your example:
# entering this context actually does nothing
with conn:
# a transaction is magically created before this statement
conn.execute("insert into a values (1)")
# and is implicitly committed before this statement
conn.execute("SAVEPOINT sp1")
# a new transaction is magically created
conn.execute("insert into a values (2)")
# and committed, discarding the first savepoint.
conn.execute("SAVEPOINT sp2")
# a new transaction is magically created
conn.execute("insert into a values (3)")
# and committed, discarding the very savepoint we are trying to use.
conn.execute("ROLLBACK TO sp2")
conn.execute("insert into a values (4)")
conn.execute("RELEASE sp1")
We all know the Zen of Python. Explicit is better than implicit.
There is no point in using a savepoint outside a transaction. There is
no point in using a savepoint if it commits all previous changes
automatically.
Conclusion:
Sqlite's isolation_level is dark magic. It mixes real isolation levels
with behaviour of context managers, and automagical commits in the wrong
places.
Setting isolation_level=None is a must for anyone who want to do any
serious work with sqlite.
L
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