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.

Spigot-Server-Patches/0432-Optimize-Persistent-Data-Loading.patch

@@ -0,0 +1,56 @@
+From b5f9f16cf0a99f16d1749a3982d87ea482fd7099 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 8d51af286..e86d382c8 100644
+--- a/src/main/java/net/minecraft/server/WorldPersistentData.java
++++ b/src/main/java/net/minecraft/server/WorldPersistentData.java
+@@ -39,6 +39,7 @@ public class WorldPersistentData {
+ 
+     @Nullable
+     public <T extends PersistentBase> T a(Function<String, T> function, 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.e != null) {
+@@ -49,14 +50,15 @@ public class WorldPersistentData {
+                     persistentbase = function.apply(s); // Paper - decompile fix
+                     persistentbase.a(a(this.e, this.b, s, 1631).getCompound("data"));
+                     this.data.put(s, persistentbase);
+-                }
++                } else this.data.put(s, NO_RESULT); // Paper
+             } catch (Exception exception) {
+                 WorldPersistentData.a.error("Error loading saved data: {}", s, exception);
+             }
+         }
+ 
+-        return persistentbase;
++        return persistentbase == NO_RESULT ? null : persistentbase; // Paper
+     }
++    private static final PersistentBase NO_RESULT = new ForcedChunk("chunks"); // Paper
+ 
+     public void a(String s, PersistentBase persistentbase) {
+         this.data.put(s, persistentbase);
+@@ -126,6 +128,7 @@ public class WorldPersistentData {
+     }
+ 
+     public static NBTTagCompound a(IDataManager idatamanager, DimensionManager dimensionmanager, String s, int i) throws IOException {
++        if ("Mineshaft".equals(s) || "Mineshaft_index".equals(s)) return new NBTTagCompound(); // Paper
+         File file = idatamanager.getDataFile(dimensionmanager, s);
+         FileInputStream fileinputstream = new FileInputStream(file);
+         Throwable throwable = null;
+-- 
+2.21.0
+