Are there compatible issues when upgrading runtime have changed Storage name or structure?

[hackfisher]

Shouldn't there be a migration design just like db migration?

[AurevoirXavier]

Could you explain it in more detail? So we can build a testing env for this.

[sekisamu]

I guess, for now, we could only do it in a 'smart-contract-upgrade' way.

[hackfisher]

Could you explain it in more detail? So we can build a testing env for this.

For example, In Balances Module:

The current ReserveBalance is as following:

pub ReservedBalance get(fn reserved_balance): map T::AccountId => T::Balance;

What if we change the name of ReservedBalance to ReservedX, or change the type of map to vec etc. The underline storage keys might be changed or broken then.

I guess we may meet such migration challenges in future mainet upgrading process, and asking for the best practice.

In worst case, we could do migration through Extrinsics, just like Ethereum TXs?

[hackfisher]

Migrate example:

https://github.com/paritytech/substrate/blob/master/frame/staking/src/migration.rs

[AurevoirXavier]

First try in #218