Paper/patches/server/0349-Optimize-Hoppers.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 27 Apr 2016 22:09:52 -0400
Subject: [PATCH] Optimize Hoppers

* Removes unnecessary extra calls to .update() that are very expensive
* Lots of itemstack cloning removed. Only clone if the item is actually moved
* Return true when a plugin cancels inventory move item event instead of false, as false causes pulls to cycle through all items.
  However, pushes do not exhibit the same behavior, so this is not something plugins could of been relying on.
* Add option (Default on) to cooldown hoppers when they fail to move an item due to full inventory
* Skip subsequent InventoryMoveItemEvents if a plugin does not use the item after first event fire for an iteration
* Don't check for Entities with Inventories if the block above us is also occluding (not just Inventoried)
* Remove Streams from Item Suck In and restore restore 1.12 AABB checks which is simpler and no voxel allocations (was doing TWO Item Suck ins)

diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
index 8190c30346c0fd2d86fb7cbcfc7ce17333e05146..041efecbfcd54384d15ebf771cdfa0e711483997 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
@@ -431,5 +431,14 @@ public class PaperWorldConfig {
     private void entitiesTargetWithFollowRange() {
         entitiesTargetWithFollowRange = getBoolean("entities-target-with-follow-range", entitiesTargetWithFollowRange);
     }
+
+    public boolean cooldownHopperWhenFull = true;
+    public boolean disableHopperMoveEvents = false;
+    private void hopperOptimizations() {
+        cooldownHopperWhenFull = getBoolean("hopper.cooldown-when-full", cooldownHopperWhenFull);
+        log("Cooldown Hoppers when Full: " + (cooldownHopperWhenFull ? "enabled" : "disabled"));
+        disableHopperMoveEvents = getBoolean("hopper.disable-move-event", disableHopperMoveEvents);
+        log("Hopper Move Item Events: " + (disableHopperMoveEvents ? "disabled" : "enabled"));
+    }
 }
 
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index f00839eab02277bf10b742c88fadc4aa9e89e7e0..312be2221e1acc44aaf6936533b0eb968f796dc6 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -1422,6 +1422,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         while (iterator.hasNext()) {
             ServerLevel worldserver = (ServerLevel) iterator.next();
             worldserver.hasPhysicsEvent =  org.bukkit.event.block.BlockPhysicsEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper
+            net.minecraft.world.level.block.entity.HopperBlockEntity.skipHopperEvents = worldserver.paperConfig.disableHopperMoveEvents || org.bukkit.event.inventory.InventoryMoveItemEvent.getHandlerList().getRegisteredListeners().length == 0; // Paper
 
             this.profiler.push(() -> {
                 return worldserver + " " + worldserver.dimension().location();
diff --git a/src/main/java/net/minecraft/world/item/ItemStack.java b/src/main/java/net/minecraft/world/item/ItemStack.java
index dd4deb08eb3ed15a156269a11d3d43abfd61fe5b..10f55ba189d12c46e0ef38b0b96a29894b4fba93 100644
--- a/src/main/java/net/minecraft/world/item/ItemStack.java
+++ b/src/main/java/net/minecraft/world/item/ItemStack.java
@@ -601,11 +601,12 @@ public final class ItemStack {
         return this.getItem().interactLivingEntity(this, user, entity, hand);
     }
 
-    public ItemStack copy() {
-        if (this.isEmpty()) {
+    public ItemStack copy() { return cloneItemStack(false); } // Paper
+    public ItemStack cloneItemStack(boolean origItem) { // Paper
+        if (!origItem && this.isEmpty()) { // Paper
             return ItemStack.EMPTY;
         } else {
-            ItemStack itemstack = new ItemStack(this.getItem(), this.count);
+            ItemStack itemstack = new ItemStack(origItem ? this.item : this.getItem(), this.count); // Paper
 
             itemstack.setPopTime(this.getPopTime());
             if (this.tag != null) {
diff --git a/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java
index 8a079ee3ed243fd19b1dd7eed2de1dd33785faa1..c3a07ccccd5cc38552363c82398f432c8d624288 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java
@@ -63,6 +63,7 @@ public abstract class BlockEntity implements net.minecraft.server.KeyedObject {
         getMinecraftKey(); // Try to load if it doesn't exists.
         return tileEntityKeyString;
     }
+    static boolean IGNORE_TILE_UPDATES = false;
     // Paper end
 
     @Nullable
@@ -145,6 +146,7 @@ public abstract class BlockEntity implements net.minecraft.server.KeyedObject {
 
     public void setChanged() {
         if (this.level != null) {
+            if (IGNORE_TILE_UPDATES) return; // Paper
             BlockEntity.setChanged(this.level, this.worldPosition, this.blockState);
         }
 
diff --git a/src/main/java/net/minecraft/world/level/block/entity/Hopper.java b/src/main/java/net/minecraft/world/level/block/entity/Hopper.java
index a05acf709735b40ca86f978508c63a86065fd405..c1754df6a60ff93d75a28145b9dc4e9174241a21 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/Hopper.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/Hopper.java
@@ -14,6 +14,10 @@ public interface Hopper extends Container {
         return SUCK;
     }
 
+    net.minecraft.world.level.Level getLevel();
+
+    default net.minecraft.core.BlockPos getBlockPosition() { return new net.minecraft.core.BlockPos(getLevelX(), getLevelY(), getLevelZ()); } // Paper
+
     double getLevelX();
 
     double getLevelY();
diff --git a/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
index 0ec16d554c2b51a64614c73783505c7b06ff02c7..86c0a477883102e4aebdab7ac28bf9f2ab2f7c48 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
@@ -3,7 +3,6 @@ package net.minecraft.world.level.block.entity;
 import java.util.Iterator;
 import java.util.List;
 import java.util.function.BooleanSupplier;
-import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import javax.annotation.Nullable;
 import net.minecraft.core.BlockPos;
@@ -33,7 +32,6 @@ import net.minecraft.world.level.block.state.BlockState;
 import net.minecraft.world.phys.AABB;
 import net.minecraft.world.phys.shapes.BooleanOp;
 import net.minecraft.world.phys.shapes.Shapes;
-import org.bukkit.Bukkit;
 import org.bukkit.craftbukkit.entity.CraftHumanEntity;
 import org.bukkit.craftbukkit.inventory.CraftItemStack;
 import org.bukkit.entity.HumanEntity;
@@ -192,6 +190,159 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
         return false;
     }
+    // Paper start - Optimize Hoppers
+    private static boolean skipPullModeEventFire = false;
+    private static boolean skipPushModeEventFire = false;
+    public static boolean skipHopperEvents = false;
+
+    private static boolean hopperPush(Level level, BlockPos pos, Container iinventory, Direction enumdirection, HopperBlockEntity hopper) {
+        skipPushModeEventFire = skipHopperEvents;
+        boolean foundItem = false;
+        for (int i = 0; i < iinventory.getContainerSize(); ++i) {
+            ItemStack item = iinventory.getItem(i);
+            if (!item.isEmpty()) {
+                foundItem = true;
+                ItemStack origItemStack = item;
+                ItemStack itemstack = origItemStack;
+
+                final int origCount = origItemStack.getCount();
+                final int moved = Math.min(level.spigotConfig.hopperAmount, origCount);
+                origItemStack.setCount(moved);
+
+                // We only need to fire the event once to give protection plugins a chance to cancel this event
+                // Because nothing uses getItem, every event call should end up the same result.
+                if (!skipPushModeEventFire) {
+                    itemstack = callPushMoveEvent(iinventory, itemstack, hopper);
+                    if (itemstack == null) { // cancelled
+                        origItemStack.setCount(origCount);
+                        return false;
+                    }
+                }
+                final ItemStack itemstack2 = addItem(hopper, iinventory, itemstack, enumdirection);
+                final int remaining = itemstack2.getCount();
+                if (remaining != moved) {
+                    origItemStack = origItemStack.cloneItemStack(true);
+                    origItemStack.setCount(origCount);
+                    if (!origItemStack.isEmpty()) {
+                        origItemStack.setCount(origCount - moved + remaining);
+                    }
+                    hopper.setItem(i, origItemStack);
+                    iinventory.setChanged();
+                    return true;
+                }
+                origItemStack.setCount(origCount);
+            }
+        }
+        if (foundItem && level.paperConfig.cooldownHopperWhenFull) { // Inventory was full - cooldown
+            hopper.setCooldown(level.spigotConfig.hopperTransfer);
+        }
+        return false;
+    }
+
+    private static boolean hopperPull(Hopper ihopper, Container iinventory, ItemStack origItemStack, int i) {
+        ItemStack itemstack = origItemStack;
+        final int origCount = origItemStack.getCount();
+        final Level world = ihopper.getLevel();
+        final int moved = Math.min(world.spigotConfig.hopperAmount, origCount);
+        itemstack.setCount(moved);
+
+        if (!skipPullModeEventFire) {
+            itemstack = callPullMoveEvent(ihopper, iinventory, itemstack);
+            if (itemstack == null) { // cancelled
+                origItemStack.setCount(origCount);
+                // Drastically improve performance by returning true.
+                // No plugin could of relied on the behavior of false as the other call
+                // site for IMIE did not exhibit the same behavior
+                return true;
+            }
+        }
+
+        final ItemStack itemstack2 = addItem(iinventory, ihopper, itemstack, null);
+        final int remaining = itemstack2.getCount();
+        if (remaining != moved) {
+            origItemStack = origItemStack.cloneItemStack(true);
+            origItemStack.setCount(origCount);
+            if (!origItemStack.isEmpty()) {
+                origItemStack.setCount(origCount - moved + remaining);
+            }
+            IGNORE_TILE_UPDATES = true;
+            iinventory.setItem(i, origItemStack);
+            IGNORE_TILE_UPDATES = false;
+            iinventory.setChanged();
+            return true;
+        }
+        origItemStack.setCount(origCount);
+
+        if (world.paperConfig.cooldownHopperWhenFull) {
+            cooldownHopper(ihopper);
+        }
+
+        return false;
+    }
+
+    private static ItemStack callPushMoveEvent(Container iinventory, ItemStack itemstack, HopperBlockEntity hopper) {
+        Inventory destinationInventory = getInventory(iinventory);
+        InventoryMoveItemEvent event = new InventoryMoveItemEvent(hopper.getOwner(false).getInventory(),
+            CraftItemStack.asCraftMirror(itemstack), destinationInventory, true);
+        boolean result = event.callEvent();
+        if (!event.calledGetItem && !event.calledSetItem) {
+            skipPushModeEventFire = true;
+        }
+        if (!result) {
+            cooldownHopper(hopper);
+            return null;
+        }
+
+        if (event.calledSetItem) {
+            return CraftItemStack.asNMSCopy(event.getItem());
+        } else {
+            return itemstack;
+        }
+    }
+
+    private static ItemStack callPullMoveEvent(Hopper hopper, Container iinventory, ItemStack itemstack) {
+        Inventory sourceInventory = getInventory(iinventory);
+        Inventory destination = getInventory(hopper);
+
+        InventoryMoveItemEvent event = new InventoryMoveItemEvent(sourceInventory,
+            // Mirror is safe as we no plugins ever use this item
+            CraftItemStack.asCraftMirror(itemstack), destination, false);
+        boolean result = event.callEvent();
+        if (!event.calledGetItem && !event.calledSetItem) {
+            skipPullModeEventFire = true;
+        }
+        if (!result) {
+            cooldownHopper(hopper);
+            return null;
+        }
+
+        if (event.calledSetItem) {
+            return CraftItemStack.asNMSCopy(event.getItem());
+        } else {
+            return itemstack;
+        }
+    }
+
+    private static Inventory getInventory(Container iinventory) {
+        Inventory sourceInventory;// Have to special case large chests as they work oddly
+        if (iinventory instanceof CompoundContainer) {
+            sourceInventory = new org.bukkit.craftbukkit.inventory.CraftInventoryDoubleChest((CompoundContainer) iinventory);
+        } else if (iinventory instanceof BlockEntity) {
+            sourceInventory = ((BlockEntity) iinventory).getOwner(false).getInventory();
+        } else {
+            sourceInventory = iinventory.getOwner().getInventory();
+        }
+        return sourceInventory;
+    }
+
+    private static void cooldownHopper(Hopper hopper) {
+        if (hopper instanceof HopperBlockEntity) {
+            ((HopperBlockEntity) hopper).setCooldown(hopper.getLevel().spigotConfig.hopperTransfer);
+        } else if (hopper instanceof MinecartHopper) {
+            ((MinecartHopper) hopper).setCooldown(hopper.getLevel().spigotConfig.hopperTransfer / 2);
+        }
+    }
+    // Paper end
 
     private static boolean a(Level world, BlockPos blockposition, BlockState iblockdata, Container iinventory, HopperBlockEntity hopper) { // CraftBukkit
         Container iinventory1 = HopperBlockEntity.getAttachedContainer(world, blockposition, iblockdata);
@@ -204,6 +355,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
             if (HopperBlockEntity.isFullContainer(iinventory1, enumdirection)) {
                 return false;
             } else {
+                return hopperPush(world, blockposition, iinventory, enumdirection, hopper); /* // Paper - disable rest
                 for (int i = 0; i < iinventory.getContainerSize(); ++i) {
                     if (!iinventory.getItem(i).isEmpty()) {
                         ItemStack itemstack = iinventory.getItem(i).copy();
@@ -241,7 +393,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
                     }
                 }
 
-                return false;
+                return false;*/ // Paper - end commenting out replaced block for Hopper Optimizations
             }
         }
     }
@@ -251,27 +403,68 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     }
 
     private static boolean isFullContainer(Container inventory, Direction direction) {
-        return HopperBlockEntity.getSlots(inventory, direction).allMatch((i) -> {
-            ItemStack itemstack = inventory.getItem(i);
-
-            return itemstack.getCount() >= itemstack.getMaxStackSize();
-        });
+        return allMatch(inventory, direction, STACK_SIZE_TEST); // Paper - no streams
     }
 
     private static boolean isEmptyContainer(Container inv, Direction facing) {
-        return HopperBlockEntity.getSlots(inv, facing).allMatch((i) -> {
-            return inv.getItem(i).isEmpty();
-        });
+        // Paper start
+        return allMatch(inv, facing, IS_EMPTY_TEST);
+    }
+    private static boolean allMatch(Container iinventory, Direction enumdirection, java.util.function.BiPredicate<ItemStack, Integer> test) {
+        if (iinventory instanceof WorldlyContainer) {
+            for (int i : ((WorldlyContainer) iinventory).getSlotsForFace(enumdirection)) {
+                if (!test.test(iinventory.getItem(i), i)) {
+                    return false;
+                }
+            }
+        } else {
+            int size = iinventory.getContainerSize();
+            for (int i = 0; i < size; i++) {
+                if (!test.test(iinventory.getItem(i), i)) {
+                    return false;
+                }
+            }
+        }
+        return true;
     }
 
+    private static boolean anyMatch(Container iinventory, Direction enumdirection, java.util.function.BiPredicate<ItemStack, Integer> test) {
+        if (iinventory instanceof WorldlyContainer) {
+            for (int i : ((WorldlyContainer) iinventory).getSlotsForFace(enumdirection)) {
+                if (test.test(iinventory.getItem(i), i)) {
+                    return true;
+                }
+            }
+        } else {
+            int size = iinventory.getContainerSize();
+            for (int i = 0; i < size; i++) {
+                if (test.test(iinventory.getItem(i), i)) {
+                    return true;
+                }
+            }
+        }
+        return true;
+    }
+    private static final java.util.function.BiPredicate<ItemStack, Integer> STACK_SIZE_TEST = (itemstack, i) -> itemstack.getCount() >= itemstack.getMaxStackSize();
+    private static final java.util.function.BiPredicate<ItemStack, Integer> IS_EMPTY_TEST = (itemstack, i) -> itemstack.isEmpty();
+    // Paper end
+
     public static boolean suckInItems(Level world, Hopper hopper) {
         Container iinventory = HopperBlockEntity.getSourceContainer(world, hopper);
 
         if (iinventory != null) {
             Direction enumdirection = Direction.DOWN;
 
-            return HopperBlockEntity.isEmptyContainer(iinventory, enumdirection) ? false : HopperBlockEntity.getSlots(iinventory, enumdirection).anyMatch((i) -> {
-                return HopperBlockEntity.a(hopper, iinventory, i, enumdirection, world); // Spigot
+            // Paper start - optimize hoppers and remove streams
+            skipPullModeEventFire = skipHopperEvents;
+            return !HopperBlockEntity.isEmptyContainer(iinventory, enumdirection) && anyMatch(iinventory, enumdirection, (item, i) -> {
+                // Logic copied from below to avoid extra getItem calls
+                if (!item.isEmpty() && canTakeItemFromContainer(iinventory, item, i, enumdirection)) {
+                    return hopperPull(hopper, iinventory, item, i);
+                } else {
+                    return false;
+                }
+                // Paper end
             });
         } else {
             Iterator iterator = HopperBlockEntity.getItemsAtAndAbove(world, hopper).iterator();
@@ -290,10 +483,12 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
         }
     }
 
+    // Paper - method unused as logic is inlined above
     private static boolean a(Hopper ihopper, Container iinventory, int i, Direction enumdirection, Level world) { // Spigot
         ItemStack itemstack = iinventory.getItem(i);
 
-        if (!itemstack.isEmpty() && HopperBlockEntity.canTakeItemFromContainer(iinventory, itemstack, i, enumdirection)) {
+        if (!itemstack.isEmpty() && HopperBlockEntity.canTakeItemFromContainer(iinventory, itemstack, i, enumdirection)) { // If this logic changes, update above. this is left inused incase reflective plugins
+            return hopperPull(ihopper, iinventory, itemstack, i); /* // Paper - disable rest
             ItemStack itemstack1 = itemstack.copy();
             // ItemStack itemstack2 = addItem(iinventory, ihopper, iinventory.splitStack(i, 1), (EnumDirection) null);
             // CraftBukkit start - Call event on collection of items from inventories into the hopper
@@ -330,7 +525,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
             }
 
             itemstack1.shrink(origCount - itemstack2.getCount()); // Spigot
-            iinventory.setItem(i, itemstack1);
+            iinventory.setItem(i, itemstack1);*/ // Paper - end commenting out replaced block for Hopper Optimizations
         }
 
         return false;
@@ -339,7 +534,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     public static boolean addItem(Container inventory, ItemEntity itemEntity) {
         boolean flag = false;
         // CraftBukkit start
-        InventoryPickupItemEvent event = new InventoryPickupItemEvent(inventory.getOwner().getInventory(), (org.bukkit.entity.Item) itemEntity.getBukkitEntity());
+        InventoryPickupItemEvent event = new InventoryPickupItemEvent(getInventory(inventory), (org.bukkit.entity.Item) itemEntity.getBukkitEntity()); // Paper - use getInventory() to avoid snapshot creation
         itemEntity.level.getCraftServer().getPluginManager().callEvent(event);
         if (event.isCancelled()) {
             return false;
@@ -393,7 +588,9 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
             boolean flag1 = to.isEmpty();
 
             if (itemstack1.isEmpty()) {
+                IGNORE_TILE_UPDATES = true; // Paper
                 to.setItem(slot, stack);
+                IGNORE_TILE_UPDATES = false; // Paper
                 stack = ItemStack.EMPTY;
                 flag = true;
             } else if (HopperBlockEntity.canMergeItems(itemstack1, stack)) {
@@ -444,18 +641,23 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     }
 
     public static List<ItemEntity> getItemsAtAndAbove(Level world, Hopper hopper) {
-        return (List) hopper.getSuckShape().toAabbs().stream().flatMap((axisalignedbb) -> {
-            return world.getEntitiesOfClass(ItemEntity.class, axisalignedbb.move(hopper.getLevelX() - 0.5D, hopper.getLevelY() - 0.5D, hopper.getLevelZ() - 0.5D), EntitySelector.ENTITY_STILL_ALIVE).stream();
-        }).collect(Collectors.toList());
+        // Paper start - Optimize item suck in. remove streams, restore 1.12 checks. Seriously checking the bowl?!
+        double d0 = hopper.getLevelX();
+        double d1 = hopper.getLevelY();
+        double d2 = hopper.getLevelZ();
+        AABB bb = new AABB(d0 - 0.5D, d1, d2 - 0.5D, d0 + 0.5D, d1 + 1.5D, d2 + 0.5D);
+        return world.getEntitiesOfClass(ItemEntity.class, bb, Entity::isAlive);
+        // Paper end
     }
 
     @Nullable
     public static Container getContainerAt(Level world, BlockPos pos) {
-        return HopperBlockEntity.getContainerAt(world, (double) pos.getX() + 0.5D, (double) pos.getY() + 0.5D, (double) pos.getZ() + 0.5D);
+        return HopperBlockEntity.getContainerAt(world, (double) pos.getX() + 0.5D, (double) pos.getY() + 0.5D, (double) pos.getZ() + 0.5D, true); // Paper
     }
 
+    public static Container getContainerAt(Level world, double x, double y, double z) { return getContainerAt(world, x, y, z, false); } // Paper - overload to default false
     @Nullable
-    private static Container getContainerAt(Level world, double x, double y, double z) {
+    private static Container getContainerAt(Level world, double x, double y, double z, boolean optimizeEntities) {
         Object object = null;
         BlockPos blockposition = new BlockPos(x, y, z);
         if ( !world.hasChunkAt( blockposition ) ) return null; // Spigot
@@ -475,7 +677,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
             }
         }
 
-        if (object == null) {
+        if (object == null && (!optimizeEntities || !org.bukkit.craftbukkit.util.CraftMagicNumbers.getMaterial(block).isOccluding())) { // Paper
             List<Entity> list = world.getEntities((Entity) null, new AABB(x - 0.5D, y - 0.5D, z - 0.5D, x + 0.5D, y + 0.5D, z + 0.5D), EntitySelector.CONTAINER_ENTITY_SELECTOR);
 
             if (!list.isEmpty()) {
diff --git a/src/main/java/net/minecraft/world/level/block/entity/RandomizableContainerBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/RandomizableContainerBlockEntity.java
index f23fff80d07ac7d06715efe67cb49ebbe704967b..ed3518fe7c841d9e1a9c97626acaa3d765a6d76f 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/RandomizableContainerBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/RandomizableContainerBlockEntity.java
@@ -95,12 +95,19 @@ public abstract class RandomizableContainerBlockEntity extends BaseContainerBloc
     @Override
     public boolean isEmpty() {
         this.unpackLootTable((Player)null);
-        return this.getItems().stream().allMatch(ItemStack::isEmpty);
+        // Paper start
+        for (ItemStack itemStack : this.getItems()) {
+            if (!itemStack.isEmpty()) {
+                return false;
+            }
+        }
+        // Paper end
+        return true;
     }
 
     @Override
     public ItemStack getItem(int slot) {
-        this.unpackLootTable((Player)null);
+        if (slot == 0) this.unpackLootTable((Player) null); // Paper
         return this.getItems().get(slot);
     }