From 661b3fdfedfcf4fc5b67e53a902333faf3de35f4 Mon Sep 17 00:00:00 2001
From: Arya <aryasolhi@gmail.com>
Date: Wed, 24 Apr 2024 13:36:44 -0400
Subject: [PATCH] Adds a comment about avoiding duplicate ncts and avoids
 spawning rayon scope if there are no notes

---
 zebra-chain/src/parallel/tree.rs | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/zebra-chain/src/parallel/tree.rs b/zebra-chain/src/parallel/tree.rs
index e194411ea..50183cddd 100644
--- a/zebra-chain/src/parallel/tree.rs
+++ b/zebra-chain/src/parallel/tree.rs
@@ -79,8 +79,19 @@ impl NoteCommitmentTrees {
         let mut sapling_result = None;
         let mut orchard_result = None;
 
+        // Note: Only updating the note commitment trees when there are more notes that
+        //       need to be appended to the tree prevents unnecessarily duplicating note commitment
+        //       tree data in the non-finalized state.
+        let has_sprout_notes = !sprout_note_commitments.is_empty();
+        let has_sapling_notes = !sapling_note_commitments.is_empty();
+        let has_orchard_notes = !orchard_note_commitments.is_empty();
+
+        if !(has_sprout_notes || has_sapling_notes || has_orchard_notes) {
+            return Ok(());
+        }
+
         rayon::in_place_scope_fifo(|scope| {
-            if !sprout_note_commitments.is_empty() {
+            if has_sprout_notes {
                 scope.spawn_fifo(|_scope| {
                     sprout_result = Some(Self::update_sprout_note_commitment_tree(
                         sprout,
@@ -89,7 +100,7 @@ impl NoteCommitmentTrees {
                 });
             }
 
-            if !sapling_note_commitments.is_empty() {
+            if has_sapling_notes {
                 scope.spawn_fifo(|_scope| {
                     sapling_result = Some(Self::update_sapling_note_commitment_tree(
                         sapling,
@@ -98,7 +109,7 @@ impl NoteCommitmentTrees {
                 });
             }
 
-            if !orchard_note_commitments.is_empty() {
+            if has_orchard_notes {
                 scope.spawn_fifo(|_scope| {
                     orchard_result = Some(Self::update_orchard_note_commitment_tree(
                         orchard,