substrate数据迁移实例

迁移multisig数据

fn on_runtime_upgrade() -> Weight {
            // Utility.Multisigs -> Multisig.Multisigs
            use frame_support::migration::{StorageIterator, put_storage_value};
            for (key, value) in StorageIterator::<
                Multisig<T::BlockNumber, BalanceOf<T>, T::AccountId>
            >::new(b"Utility", b"Multisigs").drain() {
                put_storage_value(b"Multisig", b"Multisigs", &key, value);
            }
            1_000_000_000
        }

分析：这个是更改模块名字时候进行的数据迁移

democracy模块迁移

fn on_runtime_upgrade() -> Weight {
            if let None = StorageVersion::get() {
                StorageVersion::put(Releases::V1);

                DepositOf::<T>::translate::<
                    (BalanceOf<T>, Vec<T::AccountId>), _
                >(|_, (balance, accounts)| {
                    Some((accounts, balance))
                });

                T::MaximumBlockWeight::get()
            } else {
                T::DbWeight::get().reads(1)
            }
        }

分析: 这个应该是value值交换

indices模块

fn on_runtime_upgrade() -> Weight {
            use frame_support::migration::{StorageIterator, put_storage_value};
            for (key, value) in StorageIterator::<
                (T::AccountId, BalanceOf<T>)
            >::new(b"Indices", b"Accounts").drain() {
                put_storage_value(b"Indices", b"Accounts", &key, (value.0, value.1, false));
            }
            1_000_000_000
        }

staking模块

fn on_runtime_upgrade() -> Weight {
            #[allow(dead_code)]
            mod inner {
                pub struct Module<T>(sp_std::marker::PhantomData<T>);
                frame_support::decl_storage! {
                    trait Store for Module<T: super::Trait> as Staking {
                        pub MigrateEra: Option<super::EraIndex>;
                    }
                }
            }

            if let Releases::V3_0_0 = StorageVersion::get() {
                StorageVersion::put(Releases::V4_0_0);
                inner::MigrateEra::kill();

                T::DbWeight::get().reads_writes(1, 1)
            } else {
                T::DbWeight::get().reads(1)
            }
        }