[−][src]Function exonum_merkledb::migration::flush_migration

pub fn flush_migration(fork: &mut Fork, namespace: &str)

Flushes the migration to the fork. Once the fork is merged, the migration is complete.

The following operations will be performed:

  • Migrated indexes will replace their old versions
  • Migrated indexes will be aggregated in the default namespace
  • Indexes marked with tombstones will be removed
  • Scratchpad associated with the migration will be cleared

Safety

Flushing a migration must be performed on a fork which contains the final migration changes. Not doing so may break the state aggregation in the database. A scenario when this requirement would be violated is as follows:

  1. Start a database migration in a separate thread, constructing a MigrationHelper around Arc<dyn Database>.
  2. Create a fork.
  3. Ensure that the migration is complete via some synchronization primitive.
  4. Call flush_migration on the fork from step 2.

In this scenario, a fork may not have the latest migration data because it was created before the migration is complete. The correct workflow would be to swap steps 2 and 3, i.e., first ensure that the migration is complete and then create a fork in which it will be flushed.