From e395d9bd1581d055b49d9fc185be2aca2237ebf1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=BF=97=E5=AE=87?= <hello@evanlinjin.me>
Date: Sun, 7 Jan 2024 14:39:31 +0800
Subject: [PATCH] fix(chain): avoid using `BTreeMap::append`

The implementation of `BTreeMap::append` is non-performant making
merging changesets very slow. We use `Extend::extend` instead.

Refer to:
https://github.com/rust-lang/rust/issues/34666#issuecomment-675658420
---
 crates/chain/src/keychain.rs       |  5 +++--
 crates/chain/src/tx_data_traits.rs | 12 ++++++++----
 crates/chain/src/tx_graph.rs       | 10 ++++++----
 3 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/crates/chain/src/keychain.rs b/crates/chain/src/keychain.rs
index 63972a0ade..d443ee440b 100644
--- a/crates/chain/src/keychain.rs
+++ b/crates/chain/src/keychain.rs
@@ -58,8 +58,9 @@ impl<K: Ord> Append for ChangeSet<K> {
                 *index = other_index.max(*index);
             }
         });
-
-        self.0.append(&mut other.0);
+        // We use `extend` instead of `BTreeMap::append` due to performance issues with `append`.
+        // Refer to https://github.com/rust-lang/rust/issues/34666#issuecomment-675658420
+        self.0.extend(other.0);
     }
 
     /// Returns whether the changeset are empty.
diff --git a/crates/chain/src/tx_data_traits.rs b/crates/chain/src/tx_data_traits.rs
index 5c854a9569..8fa17ff904 100644
--- a/crates/chain/src/tx_data_traits.rs
+++ b/crates/chain/src/tx_data_traits.rs
@@ -123,8 +123,10 @@ pub trait Append {
 }
 
 impl<K: Ord, V> Append for BTreeMap<K, V> {
-    fn append(&mut self, mut other: Self) {
-        BTreeMap::append(self, &mut other)
+    fn append(&mut self, other: Self) {
+        // We use `extend` instead of `BTreeMap::append` due to performance issues with `append`.
+        // Refer to https://github.com/rust-lang/rust/issues/34666#issuecomment-675658420
+        BTreeMap::extend(self, other)
     }
 
     fn is_empty(&self) -> bool {
@@ -133,8 +135,10 @@ impl<K: Ord, V> Append for BTreeMap<K, V> {
 }
 
 impl<T: Ord> Append for BTreeSet<T> {
-    fn append(&mut self, mut other: Self) {
-        BTreeSet::append(self, &mut other)
+    fn append(&mut self, other: Self) {
+        // We use `extend` instead of `BTreeMap::append` due to performance issues with `append`.
+        // Refer to https://github.com/rust-lang/rust/issues/34666#issuecomment-675658420
+        BTreeSet::extend(self, other)
     }
 
     fn is_empty(&self) -> bool {
diff --git a/crates/chain/src/tx_graph.rs b/crates/chain/src/tx_graph.rs
index ef15d7e7d8..d43c160d75 100644
--- a/crates/chain/src/tx_graph.rs
+++ b/crates/chain/src/tx_graph.rs
@@ -1271,10 +1271,12 @@ impl<A> ChangeSet<A> {
 }
 
 impl<A: Ord> Append for ChangeSet<A> {
-    fn append(&mut self, mut other: Self) {
-        self.txs.append(&mut other.txs);
-        self.txouts.append(&mut other.txouts);
-        self.anchors.append(&mut other.anchors);
+    fn append(&mut self, other: Self) {
+        // We use `extend` instead of `BTreeMap::append` due to performance issues with `append`.
+        // Refer to https://github.com/rust-lang/rust/issues/34666#issuecomment-675658420
+        self.txs.extend(other.txs);
+        self.txouts.extend(other.txouts);
+        self.anchors.extend(other.anchors);
 
         // last_seen timestamps should only increase
         self.last_seen.extend(