mnemosine.migrations.migrate

Kind: function

Signature

migrate(conn, target: int | None=None)

Documentation

Apply pending migrations to conn.

Reads PRAGMA user_version, then runs each migration whose version is greater than the stored version (and, if given, not greater than target). Each migration runs inside its own transaction so a failure rolls back cleanly; the version is bumped only after the migration body succeeds. Idempotent: calling again after a successful run is a no-op.

Args:

• conn (sqlite3.Connection): An open connection to the database.
• target (int | None): Optional upper bound version. Migrations above
• this value are skipped. None means "migrate to the latest".

Returns:

• int: The schema version that was stored before migrating (the
• current value).

Raises:

• sqlite3.Error: If any migration statement fails; the failed
• migration's transaction is rolled back first.

Example:

>>> from mnemosine.migrations import migrate, latest_version
>>> import sqlite3
>>> conn = sqlite3.connect(":memory:")
>>> migrate(conn)
0
>>> conn.execute("PRAGMA user_version").fetchone()[0] == latest_version()
True