From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Thu, 11 Mar 2021 21:17:02 -0800
Subject: [PATCH] Use hash table for maintaing changed block set

When a lot of block changes occur the iteration for checking can
add up a bit and cause a small performance impact.

diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
index 234a1eff2d664bf611c5337ee84d091b64cd7004..54cb9f909df7d1041cec553e1f54ff8ecff48bbe 100644
--- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
+++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
@@ -41,6 +41,8 @@ import net.minecraft.world.level.lighting.LevelLightEngine;
 import net.minecraft.server.MinecraftServer;
 // CraftBukkit end
 
+import it.unimi.dsi.fastutil.shorts.ShortOpenHashSet; // Paper
+
 public class ChunkHolder {
 
     public static final Either<ChunkAccess, ChunkHolder.ChunkLoadingFailure> UNLOADED_CHUNK = Either.right(ChunkHolder.ChunkLoadingFailure.UNLOADED);
@@ -390,7 +392,7 @@ public class ChunkHolder {
             if (i < 0 || i >= this.changedBlocksPerSection.length) return; // CraftBukkit - SPIGOT-6086, SPIGOT-6296
             if (this.changedBlocksPerSection[i] == null) {
                 this.hasChangedSections = true;
-                this.changedBlocksPerSection[i] = new ShortArraySet();
+                this.changedBlocksPerSection[i] = new ShortOpenHashSet(); // Paper - use a set to make setting constant-time
             }
 
             this.changedBlocksPerSection[i].add(SectionPos.sectionRelativePos(pos));