Is a "fast_unstake" call (eg. in Polkadot.js) equivalent to a "chill" followed to "unbond" (for the full stake in the stash)?

Question

I want to unstake the sum on a stash account. The classic way is to chill the account first, then to unbond the sum (and possibly to call "withdrawUnbonded" before "unbond", to free unlocking chunk slots). Could I achieve the same instead through a single call to "fast_unstake" (possibly still preceeded by a call to "withdrawUnbonded")?

Answer 1

fast_unstake is meant to be used only under certain conditions, as explained here:

If a nominator is not exposed in any ErasStakers (i.e. “has not actively backed any validators in the last BondingDuration eras”), then they can register themselves in this pallet, unstake faster than having to wait an entire bonding duration.

That being said, you are correct to think that fast_unstake, under the hood, calls chill(), then unbond(all_tokens). This is explained in the Call::register_fast_unstake section.

But, I want to warn you that using register_fast_unstake for stakers that do not qualify might result in a small slash of a deposit.

If unsuccessful, meaning that the staker was exposed sometime in the last BondingDuration eras they will end up being slashed for the amount of wasted work they have inflicted on the chian.