From 67e3c2619090c77d9bef19ade17f9012e77826e4 Mon Sep 17 00:00:00 2001
From: teor <teor@riseup.net>
Date: Sat, 26 Aug 2023 11:45:46 +1000
Subject: [PATCH] Avoid expensive cryptographic tree root recalculations in
 eq() (#7386)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
---
 zebra-chain/src/orchard/tree.rs | 8 +++++++-
 zebra-chain/src/sapling/tree.rs | 8 +++++++-
 zebra-chain/src/sprout/tree.rs  | 8 +++++++-
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/zebra-chain/src/orchard/tree.rs b/zebra-chain/src/orchard/tree.rs
index 9862bd8f..8a2acf5b 100644
--- a/zebra-chain/src/orchard/tree.rs
+++ b/zebra-chain/src/orchard/tree.rs
@@ -428,7 +428,13 @@ impl Eq for NoteCommitmentTree {}
 
 impl PartialEq for NoteCommitmentTree {
     fn eq(&self, other: &Self) -> bool {
-        self.hash() == other.hash()
+        if let (Some(root), Some(other_root)) = (self.cached_root(), other.cached_root()) {
+            // Use cached roots if available
+            root == other_root
+        } else {
+            // Avoid expensive root recalculations which use multiple cryptographic hashes
+            self.inner == other.inner
+        }
     }
 }
 
diff --git a/zebra-chain/src/sapling/tree.rs b/zebra-chain/src/sapling/tree.rs
index 5b5bed23..75eea88e 100644
--- a/zebra-chain/src/sapling/tree.rs
+++ b/zebra-chain/src/sapling/tree.rs
@@ -423,7 +423,13 @@ impl Eq for NoteCommitmentTree {}
 
 impl PartialEq for NoteCommitmentTree {
     fn eq(&self, other: &Self) -> bool {
-        self.hash() == other.hash()
+        if let (Some(root), Some(other_root)) = (self.cached_root(), other.cached_root()) {
+            // Use cached roots if available
+            root == other_root
+        } else {
+            // Avoid expensive root recalculations which use multiple cryptographic hashes
+            self.inner == other.inner
+        }
     }
 }
 
diff --git a/zebra-chain/src/sprout/tree.rs b/zebra-chain/src/sprout/tree.rs
index 2b70b0a3..5c926928 100644
--- a/zebra-chain/src/sprout/tree.rs
+++ b/zebra-chain/src/sprout/tree.rs
@@ -377,7 +377,13 @@ impl Eq for NoteCommitmentTree {}
 
 impl PartialEq for NoteCommitmentTree {
     fn eq(&self, other: &Self) -> bool {
-        self.hash() == other.hash()
+        if let (Some(root), Some(other_root)) = (self.cached_root(), other.cached_root()) {
+            // Use cached roots if available
+            root == other_root
+        } else {
+            // Avoid expensive root recalculations which use multiple cryptographic hashes
+            self.inner == other.inner
+        }
     }
 }