def migrate(memo_type: type) -> None

Apply pending tag-field schema migration for a memo type.

Use db0.migrate(...) when automatic tag-field migration is disabled with no_auto_migrate=True and the running class declaration differs from the declaration stored in the prefix.

Parameters

• memo_type type
  The @db0.memo class whose pending tag-field declaration should be applied.

Returns

This function does not return a value.

Example

import dbzero as db0
 
db0.init("/var/lib/my-app/dbzero", no_auto_migrate=True)
db0.open("main")
 
@db0.tag_fields("status")
@db0.memo
class Task:
    def __init__(self, status):
        self.status = status
 
try:
    Task("open")
except db0.MigrateError:
    db0.migrate(Task)

After db0.migrate(Task) completes, the current @db0.tag_fields(...) declaration becomes active for that type. Existing objects are retagged according to the new declaration, and future assignments use the new tag-field settings.

If migration fails, the previous declaration remains active.