Interface GasCostSummary

Summary of the charges in a transaction. Storage is charged independently of computation. There are 3 parts to the storage charges: storage_cost: it is the charge of storage at the time the transaction is executed. The cost of storage is the number of bytes of the objects being mutated multiplied by a variable storage cost per byte storage_rebate: this is the amount a user gets back when manipulating an object. The storage_rebate is the storage_cost for an object minus fees. non_refundable_storage_fee: not all the value of the object storage cost is given back to user and there is a small fraction that is kept by the system. This value tracks that charge.

When looking at a gas cost summary the amount charged to the user is computation_cost + storage_cost - storage_rebate and that is the amount that is deducted from the gas coins. non_refundable_storage_fee is collected from the objects being mutated/deleted and it is tracked by the system in storage funds.

Objects deleted, including the older versions of objects mutated, have the storage field on the objects added up to a pool of "potential rebate". This rebate then is reduced by the "nonrefundable rate" such that: potential_rebate(storage cost of deleted/mutated objects) = storage_rebate + non_refundable_storage_fee