From e1ed8abcbc9786fcffb960f9f44426bffe13d9f6 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Fri, 29 Mar 2019 01:25:11 -0400
Subject: [PATCH] Optimize Persistent Data Loading

removes Mineshaft loading legacy as we had pre 1.13.2 to avoid managing
that very large data file from legacy systems.

Previous to 1.13.2 these data files were never loaded to begin with, so they
effectively do not contain valid/relevant data.

These files take a long time to convert on large worlds and crashes the server.

Additionally, cache the result of a file being missing so we don't keep spam checking it.

diff --git a/src/main/java/net/minecraft/server/WorldPersistentData.java b/src/main/java/net/minecraft/server/WorldPersistentData.java
index 47a4ea998..62081349f 100644
--- a/src/main/java/net/minecraft/server/WorldPersistentData.java
+++ b/src/main/java/net/minecraft/server/WorldPersistentData.java
@@ -26,6 +26,7 @@ public class WorldPersistentData {
         this.c = datafixer;
         this.d = file;
     }
+    private static final PersistentBase NO_RESULT = new ForcedChunk(); // Paper
 
     private File a(String s) {
         return new File(this.d, s + ".dat");
@@ -46,6 +47,7 @@ public class WorldPersistentData {
 
     @Nullable
     public <T extends PersistentBase> T b(Supplier<T> supplier, String s) {
+        if ("Mineshaft_index".equals(s) || "Mineshaft".equals(s)) return null; // Paper - mineshaft is useless data
         PersistentBase persistentbase = (PersistentBase) this.data.get(s);
 
         if (persistentbase == null) {
@@ -58,13 +60,13 @@ public class WorldPersistentData {
 
                     persistentbase.a(nbttagcompound.getCompound("data"));
                     this.data.put(s, persistentbase);
-                }
+                } else this.data.put(s, NO_RESULT); // Paper
             } catch (Exception exception) {
                 WorldPersistentData.LOGGER.error("Error loading saved data: {}", s, exception);
             }
         }
 
-        return (T) persistentbase; // Paper - decompile fix
+        return (T) persistentbase == NO_RESULT ? null : (T) persistentbase; // Paper - decompile fix // Paper
     }
 
     public void a(PersistentBase persistentbase) {
@@ -72,6 +74,7 @@ public class WorldPersistentData {
     }
 
     public NBTTagCompound a(String s, int i) throws IOException {
+        if ("Mineshaft".equals(s) || "Mineshaft_index".equals(s)) return new NBTTagCompound(); // Paper
         File file = this.a(s);
         PushbackInputStream pushbackinputstream = new PushbackInputStream(new FileInputStream(file), 2);
         Throwable throwable = null;
-- 
2.21.0