In the runtime chain extension, should we be charging weight if we are reading a `StorageMap`?

Question

If we have the storage map DummyStorageMap in pallet-example

And we read its value under the key key by calling DummyStorageMap::<T>::get(key) in the runtime chain extension (https://paritytech.github.io/substrate/master/pallet_contracts/chain_extension/trait.ChainExtension.html#) , should we be charging weight (https://paritytech.github.io/substrate/master/pallet_contracts/chain_extension/struct.Environment.html#method.charge_weight)?

I know we are obviously supposed to charge weight if we execute an extrinsic of a pallet in the runtime chain extension, but what about if we read a storage map / storage value?

Thanks

@bkchr :)

Answer 1

If you are not doing complex calculations in your runtime, most of the time the storage reading/writing should dominate your weight. With 2D weights which also include the increase of the proof size, reading storage will be more important to your weight calculation.

So, yes you need to charge weight for only reading.