perf(store): avoid duplicate nullifier iteration

CHANGELOG.md

@@ -34,6 +34,7 @@
 - [BREAKING] Renamed `SubmitProvenBatch` RPC endpoint to `SubmitProvenTxBatch` ([#2094](https://github.com/0xMiden/node/pull/2094)).
 - Fixed block producer mempool panic when selecting transactions that depend on notes created by pruned committed transactions ([#2097](https://github.com/0xMiden/node/pull/2097)).
 - Implemented filtering based on the network account note script root allowlist in ntx-builder ([#2042](https://github.com/0xMiden/node/issues/2042)).
+- Avoided a duplicate pass over block nullifiers while computing store tree mutations ([#1548](https://github.com/0xMiden/node/issues/1548)).
 
 - [BREAKING] Renamed `ExplorerStatusDetails` fields in the network monitor's `/status` payload from `number_of_*` to `total_*` (`total_transactions`, `total_nullifiers`, `total_notes`, `total_account_updates`). The values now represent network-wide cumulative totals from the explorer's `overviewStats` query instead of last-block counts.
 - [BREAKING] Removed `--wallet-filepath` / `--counter-filepath` flags and the `MIDEN_MONITOR_WALLET_FILEPATH` / `MIDEN_MONITOR_COUNTER_FILEPATH` env vars from the network monitor. The monitor now keeps wallet and counter accounts fully in memory and regenerates them on every startup; the dashboard's counter value resets to zero on restart.

crates/store/src/state/apply_block.rs

@@ -221,12 +221,18 @@ impl State {
         self.with_inner_read_blocking(|inner| {
             let block_num = header.block_num();
 
-            // nullifiers can be produced only once
-            let duplicate_nullifiers: Vec<_> = body
+            // Nullifiers can be produced only once. Build the mutation input in the same pass so
+            // large blocks do not need to traverse the nullifier list twice.
+            let mut duplicate_nullifiers = Vec::new();
+            let nullifier_mutations: Vec<_> = body
                 .created_nullifiers()
                 .iter()
-                .filter(|&nullifier| inner.nullifier_tree.get_block_num(nullifier).is_some())
-                .copied()
+                .map(|nullifier| {
+                    if inner.nullifier_tree.get_block_num(nullifier).is_some() {
+                        duplicate_nullifiers.push(*nullifier);
+                    }
+                    (*nullifier, block_num)
+                })
                 .collect();
             if !duplicate_nullifiers.is_empty() {
                 return Err(InvalidBlockError::DuplicatedNullifiers(duplicate_nullifiers).into());
@@ -241,9 +247,7 @@ impl State {
             // compute update for nullifier tree
             let nullifier_tree_update = inner
                 .nullifier_tree
-                .compute_mutations(
-                    body.created_nullifiers().iter().map(|nullifier| (*nullifier, block_num)),
-                )
+                .compute_mutations(nullifier_mutations)
                 .map_err(InvalidBlockError::NewBlockNullifierAlreadySpent)?;
 
             if nullifier_tree_update.as_mutation_set().root() != header.nullifier_root() {