From 73910a70767c433e84e39baa0d0de23ef4d99738 Mon Sep 17 00:00:00 2001
From: HaoranYi <haoran.yi@solana.com>
Date: Tue, 24 Oct 2023 15:04:17 +0000
Subject: [PATCH 1/2] optimize account hash merkle tree index from vec to
 2-element array

---
 accounts-db/src/accounts_hash.rs | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/accounts-db/src/accounts_hash.rs b/accounts-db/src/accounts_hash.rs
index e9f25b318d5a4b..717603ee33d5c1 100644
--- a/accounts-db/src/accounts_hash.rs
+++ b/accounts-db/src/accounts_hash.rs
@@ -334,7 +334,8 @@ const _: () = assert!(
 
 #[derive(Default, Debug, PartialEq, Eq)]
 pub struct CumulativeOffset {
-    pub index: Vec<usize>,
+    /// Since the source data in at most 2D, two indexes are enough.
+    pub index: [usize; 2],
     pub start_offset: usize,
 }
 
@@ -416,7 +417,7 @@ impl CumulativeOffsets {
             .filter_map(|(i, len)| {
                 if len > 0 {
                     let result = CumulativeOffset {
-                        index: vec![i],
+                        index: [i, i],
                         start_offset: total_count,
                     };
                     total_count += len;
@@ -1373,7 +1374,7 @@ mod tests {
                             cumulative_offsets = Vec::with_capacity(raw.len() * v_outer.len());
                         }
                         cumulative_offsets.push(CumulativeOffset {
-                            index: vec![i, j],
+                            index: [i, j],
                             start_offset: total_count,
                         });
                         total_count += len;
@@ -2126,7 +2127,7 @@ mod tests {
     fn test_accountsdb_cumulative_find() {
         let input = CumulativeOffsets {
             cumulative_offsets: vec![CumulativeOffset {
-                index: vec![0],
+                index: [0; 2],
                 start_offset: 0,
             }],
             total_count: 0,
@@ -2136,11 +2137,11 @@ mod tests {
         let input = CumulativeOffsets {
             cumulative_offsets: vec![
                 CumulativeOffset {
-                    index: vec![0],
+                    index: [0; 2],
                     start_offset: 0,
                 },
                 CumulativeOffset {
-                    index: vec![1],
+                    index: [1; 2],
                     start_offset: 2,
                 },
             ],

From 911c9d9a53c2f1cf91cf1a49f463334c03b2e2ad Mon Sep 17 00:00:00 2001
From: HaoranYi <haoran.yi@solana.com>
Date: Tue, 24 Oct 2023 17:25:20 +0000
Subject: [PATCH 2/2] typo

---
 accounts-db/src/accounts_hash.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/accounts-db/src/accounts_hash.rs b/accounts-db/src/accounts_hash.rs
index 717603ee33d5c1..d5b3d34b0f7d01 100644
--- a/accounts-db/src/accounts_hash.rs
+++ b/accounts-db/src/accounts_hash.rs
@@ -334,7 +334,7 @@ const _: () = assert!(
 
 #[derive(Default, Debug, PartialEq, Eq)]
 pub struct CumulativeOffset {
-    /// Since the source data in at most 2D, two indexes are enough.
+    /// Since the source data is at most 2D, two indexes are enough.
     pub index: [usize; 2],
     pub start_offset: usize,
 }