refactor(migration-canister): cache last event for every migration #7948
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Co-authored-by: michael-weigelt <122277901+michael-weigelt@users.noreply.github.com>
michael-weigelt
approved these changes
Dec 9, 2025
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This PR refactors the stable memory representation of events in the migration canister to
Alternatives considered:
BTreeMap<CanisterMigrationArgs, Vec<Event>, Memory>- this representation is inefficient if there are (maliciously) many events for a given pair of source and target canisters;BTreeMap<Event, (), Memory>with events sorted by their pairs of source and target canisters - relying on range queries is fragile and introduces substantial complexity for testing.