From 4f23ede23ade4b6f09398c7b12f6044ad88914d7 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Fri, 28 Sep 2018 20:46:29 -0400
Subject: [PATCH] Optimize Light Recalculations

The server triggers light recalculations even if the new block
is the same as the old block. At this time, BlockData Properties
do not impact light calculations.

So the only way light should change, is if the block itself
changes from 1 block to another.

diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
index 53aab97866..e4bda70bb9 100644
--- a/src/main/java/net/minecraft/server/Chunk.java
+++ b/src/main/java/net/minecraft/server/Chunk.java
@@ -578,7 +578,7 @@ public class Chunk implements IChunkAccess {
             } else {
                 if (flag1) {
                     this.initLighting();
-                } else {
+                } else if (block != block1) { // Paper - Optimize light recalculations
                     this.runOrQueueLightUpdate(() -> { // Paper - Queue light update
                     int i1 = iblockdata.b(this.world, blockposition);
                     int j1 = iblockdata1.b(this.world, blockposition);
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index 13f69f1b82..763401835d 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -444,7 +444,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
             } else {
                 IBlockData iblockdata2 = this.getType(blockposition);
 
-                if (iblockdata2.b(this, blockposition) != iblockdata1.b(this, blockposition) || iblockdata2.e() != iblockdata1.e()) {
+                if (iblockdata.getBlock() != iblockdata2.getBlock() && iblockdata2.b(this, blockposition) != iblockdata1.b(this, blockposition) || iblockdata2.e() != iblockdata1.e()) { // Paper - optimize light recalculations
                     this.methodProfiler.a("checkLight");
                     chunk.runOrQueueLightUpdate(() -> this.r(blockposition)); // Paper - Queue light update
                     this.methodProfiler.e();
-- 
2.19.0