Remove dead code related to migration

rs/backend/nns-dapp-exports-production.txt

@@ -21,5 +21,4 @@ canister_update register_hardware_wallet
 canister_update rename_canister
 canister_update rename_sub_account
 canister_update set_imported_tokens
-canister_update step_migration
 main

rs/backend/nns-dapp-exports-test.txt

@@ -23,5 +23,4 @@ canister_update register_hardware_wallet
 canister_update rename_canister
 canister_update rename_sub_account
 canister_update set_imported_tokens
-canister_update step_migration
 main

rs/backend/nns-dapp.did

@@ -238,8 +238,6 @@ service: (opt Config) -> {
     http_request: (request: HttpRequest) -> (HttpResponse) query;
     add_stable_asset: (asset: blob) -> ();
 
-    step_migration: (nat32) -> ();
-
     // Methods available in the test build only:
     create_toy_accounts: (nat) -> (nat64);
     get_toy_account: (nat64) -> (GetAccountResponse) query;

rs/backend/src/accounts_store.rs

@@ -333,18 +333,6 @@ impl AccountsStore {
         }
     }
 
-    /// Determines whether a migration is being performed.
-    #[must_use]
-    #[allow(dead_code)]
-    pub fn migration_in_progress(&self) -> bool {
-        self.accounts_db.migration_in_progress()
-    }
-    /// Advances the migration by one step.
-    ///
-    /// Note: This is a pass-through to the underlying `AccountsDb::step_migration`.  Please see that for further details.
-    pub fn step_migration(&mut self, step_size: u32) {
-        self.accounts_db.step_migration(step_size);
-    }
     #[must_use]
     pub fn get_account(&self, caller: PrincipalId) -> Option<AccountDetails> {
         let account_identifier = AccountIdentifier::from(caller);
@@ -681,7 +669,7 @@ impl AccountsStore {
         stats.accounts_count = self.accounts_db.db_accounts_len();
         stats.sub_accounts_count = self.accounts_db_stats.sub_accounts_count;
         stats.hardware_wallet_accounts_count = self.accounts_db_stats.hardware_wallet_accounts_count;
-        stats.migration_countdown = Some(self.accounts_db.migration_countdown());
+        stats.migration_countdown = Some(0);
     }
 
     #[must_use]

rs/backend/src/accounts_store/schema.rs

@@ -7,11 +7,7 @@ pub mod proxy;
 
 // Mechanics
 use crate::accounts_store::Account;
-use candid::{CandidType, Deserialize};
 use core::ops::RangeBounds;
-use serde::Serialize;
-use strum_macros::EnumIter;
-mod label_serialization;
 #[cfg(test)]
 pub mod tests;
 
@@ -114,38 +110,6 @@ pub trait AccountsDbTrait {
     fn range(&self, key_range: impl RangeBounds<Vec<u8>>) -> Box<dyn Iterator<Item = (Vec<u8>, Account)> + '_>;
 }
 
-/// A label to identify the schema.
-///
-/// Note: The numeric representations of these labels are guaranteed to be stable.
-#[repr(u32)]
-#[derive(Clone, Copy, Debug, EnumIter, PartialEq, Eq, CandidType, Serialize, Deserialize)]
-pub enum SchemaLabel {
-    /// Data is stored on the heap in a `BTreeMap` and serialized to stable memory on upgrade.
-    /// Implemented by: [`map::AccountsDbAsMap`]
-    Map = 0,
-    /// Every account is serialized separately and stored in a `StableBTreeMap`.  The remaining
-    /// data, mostly consisting of transactions, is serialized into a single large blob in the
-    /// `pre_upgrade` hook.
-    AccountsInStableMemory = 1,
-}
-
-impl Default for SchemaLabel {
-    fn default() -> Self {
-        Self::AccountsInStableMemory
-    }
-}
-
-/// Schema Label as written to stable memory.
-pub type SchemaLabelBytes = [u8; SchemaLabel::MAX_BYTES];
-
-/// Errors that can occur when de-serializing a schema label.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-pub enum SchemaLabelError {
-    InvalidChecksum,
-    InvalidLabel(u32),
-    InsufficientBytes,
-}
-
 /// A trait for data stores that support `BTreeMap` for account storage.
 #[cfg(test)]
 pub trait AccountsDbBTreeMapTrait {

rs/backend/src/accounts_store/schema/proxy.rs

@@ -3,27 +3,17 @@
 //! The proxy manages migrations from one implementation to another.
 use super::accounts_in_unbounded_stable_btree_map::{AccountsDbAsUnboundedStableBTreeMap, ProductionMemoryType};
 use super::{map::AccountsDbAsMap, Account, AccountsDbTrait};
-use core::fmt;
 use core::ops::RangeBounds;
 
 mod enum_boilerplate;
-mod migration;
 
 /// An accounts database delegates API calls to underlying implementations.
 ///
-/// Notes:
-/// - The proxy manages migrations from one implementation to another, if applicable.
-/// - The proxy code itself will specify which databases are currently in
-///   use and how to migrate from one database to another.
-/// - It is the responsibility of the post-install hook to look at any
-///   version information and set up the db accordingly.
-///
-/// # Current data storage
-/// - Accounts are stored as a map.  No migrations are undertaken.
+/// TODO: delete this entirely, since the migration logic is removed and the delegation is
+/// unnecessary.
 #[derive(Debug)]
 pub struct AccountsDbAsProxy {
     authoritative_db: AccountsDb,
-    migration: Option<Migration>,
 }
 
 impl Default for AccountsDbAsProxy {
@@ -32,27 +22,9 @@ impl Default for AccountsDbAsProxy {
     }
 }
 
-struct Migration {
-    /// The database being migrated to
-    db: AccountsDb,
-    /// The next account to migrate.
-    next_to_migrate: Option<Vec<u8>>,
-}
-
-impl fmt::Debug for Migration {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        // Note: The `next_to_migrate` field is rarely interesting so is omitted.
-        //       The database type and number of entries suffices.
-        self.db.fmt(f)
-    }
-}
-
 impl From<AccountsDb> for AccountsDbAsProxy {
     fn from(db: AccountsDb) -> Self {
-        AccountsDbAsProxy {
-            authoritative_db: db,
-            migration: None,
-        }
+        AccountsDbAsProxy { authoritative_db: db }
     }
 }
 
@@ -66,9 +38,6 @@ impl AccountsDbTrait for AccountsDbAsProxy {
     /// Inserts into all the underlying databases.
     fn db_insert_account(&mut self, account_key: &[u8], account: Account) {
         self.authoritative_db.db_insert_account(account_key, account.clone());
-        if let Some(migration) = &mut self.migration {
-            migration.db.db_insert_account(account_key, account);
-        }
     }
     /// Checks the authoritative database.
     fn db_contains_account(&self, account_key: &[u8]) -> bool {
@@ -81,9 +50,6 @@ impl AccountsDbTrait for AccountsDbAsProxy {
     /// Removes an account from all underlying databases.
     fn db_remove_account(&mut self, account_key: &[u8]) {
         self.authoritative_db.db_remove_account(account_key);
-        if let Some(migration) = self.migration.as_mut() {
-            migration.db.db_remove_account(account_key);
-        }
     }
     /// Gets the length from the authoritative database.
     fn db_accounts_len(&self) -> u64 {