From a576811cfbd84b86003b6d81569f8e4399447a10 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 00e9a17355..153809432c 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");
@@ -46,14 +47,17 @@ 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
         T persistentbase = (T) this.data.get(s); // Paper - decompile fix
 
         if (persistentbase == null && !this.data.containsKey(s)) {
             persistentbase = this.c(supplier, s);
             this.data.put(s, persistentbase);
+        } else { // Paper
+            this.data.put(s, NO_RESULT); // Paper
         }
 
-        return persistentbase;
+        return persistentbase == NO_RESULT ? null : persistentbase; // Paper
     }
 
     @Nullable
@@ -66,7 +70,7 @@ public class WorldPersistentData {
                 NBTTagCompound nbttagcompound = this.a(s, SharedConstants.a().getWorldVersion());
 
                 t0.a(nbttagcompound.getCompound("data"));
-                return t0;
+                return t0 == NO_RESULT ? null : t0; // Paper
             }
         } catch (Exception exception) {
             WorldPersistentData.LOGGER.error("Error loading saved data: {}", s, exception);
@@ -80,6 +84,7 @@ 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;
-- 
2.22.0