remove unnecessary storage item in length fee adjustment

Author: rphmeier

sugondat/chain/pallets/length-fee-adjustment/src/lib.rs

@@ -62,7 +62,11 @@ pub mod pallet {
 
     /// Configure the pallet by specifying the parameters and types on which it depends.
     #[pallet::config]
-    pub trait Config: frame_system::Config + pallet_transaction_payment::Config {
+    pub trait Config:
+        frame_system::Config
+        + pallet_transaction_payment::Config
+        + cumulus_pallet_parachain_system::Config
+    {
         // `targeted_length_fee_adjustment` parameters
         #[pallet::constant]
         type TransactionByteFee: Get<<<Self as pallet_transaction_payment::Config>::OnChargeTransaction as OnChargeTransaction<Self>>::Balance>;
@@ -217,16 +221,14 @@ pub mod pallet {
     impl<T: Config> OnSystemEvent for Pallet<T> {
         fn on_validation_data(data: &PersistedValidationData) {
             let relay_block_number = data.relay_parent_number;
+            let prev_relay_block_number =
+                cumulus_pallet_parachain_system::Pallet::<T>::last_relay_block_number();
 
-            let prev_relay_block_number = PrevRelayBlockNumber::<T>::get();
-            PrevRelayBlockNumber::<T>::put(relay_block_number);
-
-            // if nothing was already present then this is the first block to
-            // be executed with the fee adjustment so nothing should be done
-            let prev_relay_block_number = match prev_relay_block_number {
-                Some(prev) => prev,
-                None => return,
-            };
+            // a value of zero here implies this is the first block of the parachain. no need
+            // to do a massive fee update.
+            if prev_relay_block_number == Zero::zero() {
+                return;
+            }
 
             // It should never be negative because the relay_block_number is surely
             // greater than the para_block_number.