Merge pull request paritytech#496 from subspace/prune-receipts-relative-to-best-execution-chain-number-refactor

Minor refactoring for better readability

Author: liuchengxu

cumulus/client/cirrus-executor/src/aux_schema.rs

@@ -4,7 +4,7 @@ use codec::{Decode, Encode};
 use sc_client_api::backend::AuxStore;
 use sp_blockchain::{Error as ClientError, Result as ClientResult};
 use sp_executor::ExecutionReceipt;
-use sp_runtime::traits::{Block as BlockT, NumberFor, One, SaturatedConversion, Saturating};
+use sp_runtime::traits::{Block as BlockT, NumberFor, One, SaturatedConversion};
 use subspace_core_primitives::BlockNumber;
 
 const EXECUTION_RECEIPT_KEY: &[u8] = b"execution_receipt";
@@ -50,18 +50,17 @@ pub(super) fn write_execution_receipt<Backend: AuxStore, Block: BlockT, PBlock:
 
 	let mut new_first_saved_receipt = first_saved_receipt;
 
-	let keys_to_delete = if best_execution_chain_number.saturating_sub(first_saved_receipt) >=
-		PRUNING_DEPTH.into()
-	{
-		// `first_saved_receipt` starts from 1 instead of 0, hence `PRUNING_DEPTH` - 1.
-		new_first_saved_receipt =
-			best_execution_chain_number.saturating_sub((PRUNING_DEPTH - 1).saturated_into());
+	let mut keys_to_delete = vec![];
 
-		let mut keys_to_delete = vec![];
-		let mut to_delete_start = first_saved_receipt;
-		while to_delete_start < new_first_saved_receipt {
+	if let Some(delete_receipts_to) = best_execution_chain_number
+		.saturated_into::<BlockNumber>()
+		.checked_sub(PRUNING_DEPTH)
+	{
+		new_first_saved_receipt = Into::<NumberFor<Block>>::into(delete_receipts_to) + One::one();
+		for receipt_to_delete in first_saved_receipt.saturated_into()..=delete_receipts_to {
 			let delete_block_number_key =
-				(EXECUTION_RECEIPT_BLOCK_NUMBER, to_delete_start).encode();
+				(EXECUTION_RECEIPT_BLOCK_NUMBER, receipt_to_delete).encode();
+
 			if let Some(hashes_to_delete) =
 				load_decode::<_, Vec<Block::Hash>>(backend, delete_block_number_key.as_slice())?
 			{
@@ -70,13 +69,8 @@ pub(super) fn write_execution_receipt<Backend: AuxStore, Block: BlockT, PBlock:
 				);
 				keys_to_delete.push(delete_block_number_key);
 			}
-			to_delete_start = to_delete_start.saturating_add(One::one());
 		}
-
-		keys_to_delete
-	} else {
-		vec![]
-	};
+	}
 
 	backend.insert_aux(
 		&[