Paper/patches/server/0712-Optimise-general-POI-access.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sun, 31 Jan 2021 02:29:24 -0800
Subject: [PATCH] Optimise general POI access

There are a couple of problems with mojang's POI code.
Firstly, it's all streams. Unsurprisingly, stacking
streams on top of each other is horrible for performance
and ultimately took up half of a villager's tick!

Secondly, sometime's the search radius is large and there are
a significant number of poi entries per chunk section. Even
removing streams at this point doesn't help much. The only solution
is to start at the search point and iterate outwards. This
type of approach shows massive gains for portals, simply because
we can avoid sync loading a large area of chunks. I also tested
a massive farm I found in JellySquid's discord, which showed
to benefit significantly simply because the farm had so many
portal blocks that searching through them all was very slow.

Great care has been taken so that behavior remains identical to
vanilla, however I cannot account for oddball Stream API
implementations, if they even exist (streams can technically
be loose with iteration order in a sorted stream given its
source stream is not tagged with ordered, and mojang does not
tag the source stream as ordered). However in my testing on openjdk
there showed no difference, as expected.

This patch also specifically optimises other areas of code to
use PoiAccess. For example, some villager AI and portaling code
had to be specifically modified.

diff --git a/src/main/java/io/papermc/paper/util/PoiAccess.java b/src/main/java/io/papermc/paper/util/PoiAccess.java
new file mode 100644
index 0000000000000000000000000000000000000000..1e7be5da4907616ad9e1e01a2227d29b6dd54b32
--- /dev/null
+++ b/src/main/java/io/papermc/paper/util/PoiAccess.java
@@ -0,0 +1,801 @@
+package io.papermc.paper.util;
+
+import com.mojang.datafixers.util.Pair;
+import it.unimi.dsi.fastutil.doubles.Double2ObjectMap;
+import it.unimi.dsi.fastutil.doubles.Double2ObjectRBTreeMap;
+import it.unimi.dsi.fastutil.longs.LongArrayFIFOQueue;
+import it.unimi.dsi.fastutil.longs.LongOpenHashSet;
+import java.util.function.BiPredicate;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.util.Mth;
+import net.minecraft.world.entity.ai.village.poi.PoiManager;
+import net.minecraft.world.entity.ai.village.poi.PoiRecord;
+import net.minecraft.world.entity.ai.village.poi.PoiSection;
+import net.minecraft.world.entity.ai.village.poi.PoiType;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.function.Predicate;
+
+/**
+ * Provides optimised access to POI data. All returned values will be identical to vanilla.
+ */
+public final class PoiAccess {
+
+    protected static double clamp(final double val, final double min, final double max) {
+        return (val < min ? min : (val > max ? max : val));
+    }
+
+    protected static double getSmallestDistanceSquared(final double boxMinX, final double boxMinY, final double boxMinZ,
+                                                       final double boxMaxX, final double boxMaxY, final double boxMaxZ,
+
+                                                       final double circleX, final double circleY, final double circleZ) {
+        // is the circle center inside the box?
+        if (circleX >= boxMinX && circleX <= boxMaxX && circleY >= boxMinY && circleY <= boxMaxY && circleZ >= boxMinZ && circleZ <= boxMaxZ) {
+            return 0.0;
+        }
+
+        final double boxWidthX = (boxMaxX - boxMinX) / 2.0;
+        final double boxWidthY = (boxMaxY - boxMinY) / 2.0;
+        final double boxWidthZ = (boxMaxZ - boxMinZ) / 2.0;
+
+        final double boxCenterX = (boxMinX + boxMaxX) / 2.0;
+        final double boxCenterY = (boxMinY + boxMaxY) / 2.0;
+        final double boxCenterZ = (boxMinZ + boxMaxZ) / 2.0;
+
+        double centerDiffX = circleX - boxCenterX;
+        double centerDiffY = circleY - boxCenterY;
+        double centerDiffZ = circleZ - boxCenterZ;
+
+        centerDiffX = circleX - (clamp(centerDiffX, -boxWidthX, boxWidthX) + boxCenterX);
+        centerDiffY = circleY - (clamp(centerDiffY, -boxWidthY, boxWidthY) + boxCenterY);
+        centerDiffZ = circleZ - (clamp(centerDiffZ, -boxWidthZ, boxWidthZ) + boxCenterZ);
+
+        return (centerDiffX * centerDiffX) + (centerDiffY * centerDiffY) + (centerDiffZ * centerDiffZ);
+    }
+
+
+    // key is:
+    //  upper 32 bits:
+    //   upper 16 bits: max y section
+    //   lower 16 bits: min y section
+    //  lower 32 bits:
+    //   upper 16 bits: section
+    //   lower 16 bits: radius
+    protected static long getKey(final int minSection, final int maxSection, final int section, final int radius) {
+        return (
+                (maxSection & 0xFFFFL) << (64 - 16)
+                | (minSection & 0xFFFFL) << (64 - 32)
+                | (section & 0xFFFFL) << (64 - 48)
+                | (radius & 0xFFFFL) << (64 - 64)
+                );
+    }
+
+    // only includes x/z axis
+    // finds the closest poi data by distance.
+    public static BlockPos findClosestPoiDataPosition(final PoiManager poiStorage,
+                                                      final Predicate<Holder<PoiType>> villagePlaceType,
+                                                      // position predicate must not modify chunk POI
+                                                      final Predicate<BlockPos> positionPredicate,
+                                                      final BlockPos sourcePosition,
+                                                      final int range, // distance on x y z axis
+                                                      final double maxDistance,
+                                                      final PoiManager.Occupancy occupancy,
+                                                      final boolean load) {
+        final PoiRecord ret = findClosestPoiDataRecord(
+                poiStorage, villagePlaceType, positionPredicate, sourcePosition, range, maxDistance, occupancy, load
+        );
+
+        return ret == null ? null : ret.getPos();
+    }
+
+    // only includes x/z axis
+    // finds the closest poi data by distance.
+    public static Pair<Holder<PoiType>, BlockPos> findClosestPoiDataTypeAndPosition(final PoiManager poiStorage,
+                                                                             final Predicate<Holder<PoiType>> villagePlaceType,
+                                                                             // position predicate must not modify chunk POI
+                                                                             final Predicate<BlockPos> positionPredicate,
+                                                                             final BlockPos sourcePosition,
+                                                                             final int range, // distance on x y z axis
+                                                                             final double maxDistance,
+                                                                             final PoiManager.Occupancy occupancy,
+                                                                             final boolean load) {
+        final PoiRecord ret = findClosestPoiDataRecord(
+            poiStorage, villagePlaceType, positionPredicate, sourcePosition, range, maxDistance, occupancy, load
+        );
+
+        return ret == null ? null : Pair.of(ret.getPoiType(), ret.getPos());
+    }
+
+    // only includes x/z axis
+    // finds the closest poi data by distance. if multiple match the same distance, then they all are returned.
+    public static void findClosestPoiDataPositions(final PoiManager poiStorage,
+                                                   final Predicate<Holder<PoiType>> villagePlaceType,
+                                                   // position predicate must not modify chunk POI
+                                                   final Predicate<BlockPos> positionPredicate,
+                                                   final BlockPos sourcePosition,
+                                                   final int range, // distance on x y z axis
+                                                   final double maxDistance,
+                                                   final PoiManager.Occupancy occupancy,
+                                                   final boolean load,
+                                                   final Set<BlockPos> ret) {
+        final Set<BlockPos> positions = new HashSet<>();
+        // pos predicate is last thing that runs before adding to ret.
+        final Predicate<BlockPos> newPredicate = (final BlockPos pos) -> {
+            if (positionPredicate != null && !positionPredicate.test(pos)) {
+                return false;
+            }
+            return positions.add(pos.immutable());
+        };
+
+        final List<PoiRecord> toConvert = new ArrayList<>();
+        findClosestPoiDataRecords(
+                poiStorage, villagePlaceType, newPredicate, sourcePosition, range, maxDistance, occupancy, load, toConvert
+        );
+
+        for (final PoiRecord record : toConvert) {
+            ret.add(record.getPos());
+        }
+    }
+
+    // only includes x/z axis
+    // finds the closest poi data by distance.
+    public static PoiRecord findClosestPoiDataRecord(final PoiManager poiStorage,
+                                                     final Predicate<Holder<PoiType>> villagePlaceType,
+                                                     // position predicate must not modify chunk POI
+                                                     final Predicate<BlockPos> positionPredicate,
+                                                     final BlockPos sourcePosition,
+                                                     final int range, // distance on x y z axis
+                                                     final double maxDistance,
+                                                     final PoiManager.Occupancy occupancy,
+                                                     final boolean load) {
+        final List<PoiRecord> ret = new ArrayList<>();
+        findClosestPoiDataRecords(
+            poiStorage, villagePlaceType, positionPredicate, sourcePosition, range, maxDistance, occupancy, load, ret
+        );
+        return ret.isEmpty() ? null : ret.get(0);
+    }
+
+    // only includes x/z axis
+    // finds the closest poi data by distance.
+    public static PoiRecord findClosestPoiDataRecord(final PoiManager poiStorage,
+                                                     final Predicate<Holder<PoiType>> villagePlaceType,
+                                                     // position predicate must not modify chunk POI
+                                                     final BiPredicate<Holder<PoiType>, BlockPos> predicate,
+                                                     final BlockPos sourcePosition,
+                                                     final int range, // distance on x y z axis
+                                                     final double maxDistance,
+                                                     final PoiManager.Occupancy occupancy,
+                                                     final boolean load) {
+        final List<PoiRecord> ret = new ArrayList<>();
+        findClosestPoiDataRecords(
+                poiStorage, villagePlaceType, predicate, sourcePosition, range, maxDistance, occupancy, load, ret
+        );
+        return ret.isEmpty() ? null : ret.get(0);
+    }
+
+    // only includes x/z axis
+    // finds the closest poi data by distance. if multiple match the same distance, then they all are returned.
+    public static void findClosestPoiDataRecords(final PoiManager poiStorage,
+                                                 final Predicate<Holder<PoiType>> villagePlaceType,
+                                                 // position predicate must not modify chunk POI
+                                                 final Predicate<BlockPos> positionPredicate,
+                                                 final BlockPos sourcePosition,
+                                                 final int range, // distance on x y z axis
+                                                 final double maxDistance,
+                                                 final PoiManager.Occupancy occupancy,
+                                                 final boolean load,
+                                                 final List<PoiRecord> ret) {
+        final BiPredicate<Holder<PoiType>, BlockPos> predicate = positionPredicate != null ? (type, pos) -> positionPredicate.test(pos) : null;
+        findClosestPoiDataRecords(poiStorage, villagePlaceType, predicate, sourcePosition, range, maxDistance, occupancy, load, ret);
+    }
+
+    public static void findClosestPoiDataRecords(final PoiManager poiStorage,
+                                                 final Predicate<Holder<PoiType>> villagePlaceType,
+                                                 // position predicate must not modify chunk POI
+                                                 final BiPredicate<Holder<PoiType>, BlockPos> predicate,
+                                                 final BlockPos sourcePosition,
+                                                 final int range, // distance on x y z axis
+                                                 final double maxDistance,
+                                                 final PoiManager.Occupancy occupancy,
+                                                 final boolean load,
+                                                 final List<PoiRecord> ret) {
+        final Predicate<? super PoiRecord> occupancyFilter = occupancy.getTest();
+
+        final List<PoiRecord> closestRecords = new ArrayList<>();
+        double closestDistanceSquared = maxDistance * maxDistance;
+
+        final int lowerX = Mth.floor(sourcePosition.getX() - range) >> 4;
+        final int lowerY = WorldUtil.getMinSection(poiStorage.world);
+        final int lowerZ = Mth.floor(sourcePosition.getZ() - range) >> 4;
+        final int upperX = Mth.floor(sourcePosition.getX() + range) >> 4;
+        final int upperY = WorldUtil.getMaxSection(poiStorage.world);
+        final int upperZ = Mth.floor(sourcePosition.getZ() + range) >> 4;
+
+        final int centerX = sourcePosition.getX() >> 4;
+        final int centerY = Mth.clamp(sourcePosition.getY() >> 4, lowerY, upperY);
+        final int centerZ = sourcePosition.getZ() >> 4;
+
+        final LongArrayFIFOQueue queue = new LongArrayFIFOQueue();
+        queue.enqueue(CoordinateUtils.getChunkSectionKey(centerX, centerY, centerZ));
+        final LongOpenHashSet seen = new LongOpenHashSet();
+
+        while (!queue.isEmpty()) {
+            final long key = queue.dequeueLong();
+            final int sectionX = CoordinateUtils.getChunkSectionX(key);
+            final int sectionY = CoordinateUtils.getChunkSectionY(key);
+            final int sectionZ = CoordinateUtils.getChunkSectionZ(key);
+
+            if (sectionX < lowerX || sectionX > upperX || sectionY < lowerY || sectionY > upperY || sectionZ < lowerZ || sectionZ > upperZ) {
+                // out of bound chunk
+                continue;
+            }
+
+            final double sectionDistanceSquared = getSmallestDistanceSquared(
+                    (sectionX << 4) + 0.5,
+                    (sectionY << 4) + 0.5,
+                    (sectionZ << 4) + 0.5,
+                    (sectionX << 4) + 15.5,
+                    (sectionY << 4) + 15.5,
+                    (sectionZ << 4) + 15.5,
+                    (double)sourcePosition.getX(), (double)sourcePosition.getY(), (double)sourcePosition.getZ()
+            );
+            if (sectionDistanceSquared > closestDistanceSquared) {
+                continue;
+            }
+
+            // queue all neighbours
+            for (int dz = -1; dz <= 1; ++dz) {
+                for (int dx = -1; dx <= 1; ++dx) {
+                    for (int dy = -1; dy <= 1; ++dy) {
+                        // -1 and 1 have the 1st bit set. so just add up the first bits, and it will tell us how many
+                        // values are set. we only care about cardinal neighbours, so, we only care if one value is set
+                        if ((dx & 1) + (dy & 1) + (dz & 1) != 1) {
+                            continue;
+                        }
+
+                        final int neighbourX = sectionX + dx;
+                        final int neighbourY = sectionY + dy;
+                        final int neighbourZ = sectionZ + dz;
+
+                        final long neighbourKey = CoordinateUtils.getChunkSectionKey(neighbourX, neighbourY, neighbourZ);
+                        if (seen.add(neighbourKey)) {
+                            queue.enqueue(neighbourKey);
+                        }
+                    }
+                }
+            }
+
+            final Optional<PoiSection> poiSectionOptional = load ? poiStorage.getOrLoad(key) : poiStorage.get(key);
+
+            if (poiSectionOptional == null || !poiSectionOptional.isPresent()) {
+                continue;
+            }
+
+            final PoiSection poiSection = poiSectionOptional.orElse(null);
+
+            final Map<Holder<PoiType>, Set<PoiRecord>> sectionData = poiSection.getData();
+            if (sectionData.isEmpty()) {
+                continue;
+            }
+
+            // now we search the section data
+            for (final Map.Entry<Holder<PoiType>, Set<PoiRecord>> entry : sectionData.entrySet()) {
+                if (!villagePlaceType.test(entry.getKey())) {
+                    // filter out by poi type
+                    continue;
+                }
+
+                // now we can look at the poi data
+                for (final PoiRecord poiData : entry.getValue()) {
+                    if (!occupancyFilter.test(poiData)) {
+                        // filter by occupancy
+                        continue;
+                    }
+
+                    final BlockPos poiPosition = poiData.getPos();
+
+                    if (Math.abs(poiPosition.getX() - sourcePosition.getX()) > range
+                            || Math.abs(poiPosition.getZ() - sourcePosition.getZ()) > range) {
+                        // out of range for square radius
+                        continue;
+                    }
+
+                    // it's important that it's poiPosition.distSqr(source) : the value actually is different IF the values are swapped!
+                    final double dataRange = poiPosition.distSqr(sourcePosition);
+
+                    if (dataRange > closestDistanceSquared) {
+                        // out of range for distance check
+                        continue;
+                    }
+
+                    if (predicate != null && !predicate.test(poiData.getPoiType(), poiPosition)) {
+                        // filter by position
+                        continue;
+                    }
+
+                    if (dataRange < closestDistanceSquared) {
+                        closestRecords.clear();
+                        closestDistanceSquared = dataRange;
+                    }
+                    closestRecords.add(poiData);
+                }
+            }
+        }
+
+        // uh oh! we might have multiple records that match the distance sorting!
+        // we need to re-order our results by the way vanilla would have iterated over them.
+        closestRecords.sort((record1, record2) -> {
+            // vanilla iterates the same way we do for data inside sections, so we know the ordering inside a section
+            // is fine and should be preserved (this sort is stable so we're good there)
+            // but they iterate sections by x then by z (like the following)
+            // for (int x = -dx; x <= dx; ++x)
+            //     for (int z = -dz; z <= dz; ++z)
+            //  ....
+            // so we need to reorder such that records with lower chunk z, then lower chunk x come first
+            final BlockPos pos1 = record1.getPos();
+            final BlockPos pos2 = record2.getPos();
+
+            final int cx1 = pos1.getX() >> 4;
+            final int cz1 = pos1.getZ() >> 4;
+
+            final int cx2 = pos2.getX() >> 4;
+            final int cz2 = pos2.getZ() >> 4;
+
+            if (cz2 != cz1) {
+                // want smaller z
+                return Integer.compare(cz1, cz2);
+            }
+
+            if (cx2 != cx1) {
+                // want smaller x
+                return Integer.compare(cx1, cx2);
+            }
+
+            // same chunk
+            // once vanilla has the chunk, it will iterate from all of the chunk sections starting from smaller y
+            // so now we just compare section y, wanting smaller y
+
+            return Integer.compare(pos1.getY() >> 4, pos2.getY() >> 4);
+        });
+
+        // now we match perfectly what vanilla would have outputted, without having to search the whole radius (hopefully).
+        ret.addAll(closestRecords);
+    }
+
+    // finds the closest poi entry pos.
+    public static BlockPos findNearestPoiPosition(final PoiManager poiStorage,
+                                                  final Predicate<Holder<PoiType>> villagePlaceType,
+                                                  // position predicate must not modify chunk POI
+                                                  final Predicate<BlockPos> positionPredicate,
+                                                  final BlockPos sourcePosition,
+                                                  final int range, // distance on x y z axis
+                                                  final double maxDistance,
+                                                  final PoiManager.Occupancy occupancy,
+                                                  final boolean load) {
+        final PoiRecord ret = findNearestPoiRecord(
+                poiStorage, villagePlaceType, positionPredicate, sourcePosition, range, maxDistance, occupancy, load
+        );
+        return ret == null ? null : ret.getPos();
+    }
+
+    // finds the closest `max` poi entry positions.
+    public static void findNearestPoiPositions(final PoiManager poiStorage,
+                                               final Predicate<Holder<PoiType>> villagePlaceType,
+                                               // position predicate must not modify chunk POI
+                                               final Predicate<BlockPos> positionPredicate,
+                                               final BlockPos sourcePosition,
+                                               final int range, // distance on x y z axis
+                                               final double maxDistance,
+                                               final PoiManager.Occupancy occupancy,
+                                               final boolean load,
+                                               final int max,
+                                               final List<Pair<Holder<PoiType>, BlockPos>> ret) {
+        final Set<BlockPos> positions = new HashSet<>();
+        // pos predicate is last thing that runs before adding to ret.
+        final Predicate<BlockPos> newPredicate = (final BlockPos pos) -> {
+            if (positionPredicate != null && !positionPredicate.test(pos)) {
+                return false;
+            }
+            return positions.add(pos.immutable());
+        };
+
+        final List<PoiRecord> toConvert = new ArrayList<>();
+        findNearestPoiRecords(
+                poiStorage, villagePlaceType, newPredicate, sourcePosition, range, maxDistance, occupancy, load, max, toConvert
+        );
+
+        for (final PoiRecord record : toConvert) {
+            ret.add(Pair.of(record.getPoiType(), record.getPos()));
+        }
+    }
+
+    // finds the closest poi entry.
+    public static PoiRecord findNearestPoiRecord(final PoiManager poiStorage,
+                                                 final Predicate<Holder<PoiType>> villagePlaceType,
+                                                 // position predicate must not modify chunk POI
+                                                 final Predicate<BlockPos> positionPredicate,
+                                                 final BlockPos sourcePosition,
+                                                 final int range, // distance on x y z axis
+                                                 final double maxDistance,
+                                                 final PoiManager.Occupancy occupancy,
+                                                 final boolean load) {
+        final List<PoiRecord> ret = new ArrayList<>();
+        findNearestPoiRecords(
+                poiStorage, villagePlaceType, positionPredicate, sourcePosition, range, maxDistance, occupancy, load,
+                1, ret
+        );
+        return ret.isEmpty() ? null : ret.get(0);
+    }
+
+    // finds the closest `max` poi entries.
+    public static void findNearestPoiRecords(final PoiManager poiStorage,
+                                             final Predicate<Holder<PoiType>> villagePlaceType,
+                                             // position predicate must not modify chunk POI
+                                             final Predicate<BlockPos> positionPredicate,
+                                             final BlockPos sourcePosition,
+                                             final int range, // distance on x y z axis
+                                             final double maxDistance,
+                                             final PoiManager.Occupancy occupancy,
+                                             final boolean load,
+                                             final int max,
+                                             final List<PoiRecord> ret) {
+        final Predicate<? super PoiRecord> occupancyFilter = occupancy.getTest();
+
+        final double maxDistanceSquared = maxDistance * maxDistance;
+        final Double2ObjectRBTreeMap<List<PoiRecord>> closestRecords = new Double2ObjectRBTreeMap<>();
+        int totalRecords = 0;
+        double furthestDistanceSquared = maxDistanceSquared;
+
+        final int lowerX = Mth.floor(sourcePosition.getX() - range) >> 4;
+        final int lowerY = WorldUtil.getMinSection(poiStorage.world);
+        final int lowerZ = Mth.floor(sourcePosition.getZ() - range) >> 4;
+        final int upperX = Mth.floor(sourcePosition.getX() + range) >> 4;
+        final int upperY = WorldUtil.getMaxSection(poiStorage.world);
+        final int upperZ = Mth.floor(sourcePosition.getZ() + range) >> 4;
+
+        final int centerX = sourcePosition.getX() >> 4;
+        final int centerY = Mth.clamp(sourcePosition.getY() >> 4, lowerY, upperY);
+        final int centerZ = sourcePosition.getZ() >> 4;
+
+        final LongArrayFIFOQueue queue = new LongArrayFIFOQueue();
+        queue.enqueue(CoordinateUtils.getChunkSectionKey(centerX, centerY, centerZ));
+        final LongOpenHashSet seen = new LongOpenHashSet();
+
+        while (!queue.isEmpty()) {
+            final long key = queue.dequeueLong();
+            final int sectionX = CoordinateUtils.getChunkSectionX(key);
+            final int sectionY = CoordinateUtils.getChunkSectionY(key);
+            final int sectionZ = CoordinateUtils.getChunkSectionZ(key);
+
+            if (sectionX < lowerX || sectionX > upperX || sectionY < lowerY || sectionY > upperY || sectionZ < lowerZ || sectionZ > upperZ) {
+                // out of bound chunk
+                continue;
+            }
+
+            final double sectionDistanceSquared = getSmallestDistanceSquared(
+                    (sectionX << 4) + 0.5,
+                    (sectionY << 4) + 0.5,
+                    (sectionZ << 4) + 0.5,
+                    (sectionX << 4) + 15.5,
+                    (sectionY << 4) + 15.5,
+                    (sectionZ << 4) + 15.5,
+                    (double) sourcePosition.getX(), (double) sourcePosition.getY(), (double) sourcePosition.getZ()
+            );
+
+            if (sectionDistanceSquared > (totalRecords >= max ? furthestDistanceSquared : maxDistanceSquared)) {
+                continue;
+            }
+
+            // queue all neighbours
+            for (int dz = -1; dz <= 1; ++dz) {
+                for (int dx = -1; dx <= 1; ++dx) {
+                    for (int dy = -1; dy <= 1; ++dy) {
+                        // -1 and 1 have the 1st bit set. so just add up the first bits, and it will tell us how many
+                        // values are set. we only care about cardinal neighbours, so, we only care if one value is set
+                        if ((dx & 1) + (dy & 1) + (dz & 1) != 1) {
+                            continue;
+                        }
+
+                        final int neighbourX = sectionX + dx;
+                        final int neighbourY = sectionY + dy;
+                        final int neighbourZ = sectionZ + dz;
+
+                        final long neighbourKey = CoordinateUtils.getChunkSectionKey(neighbourX, neighbourY, neighbourZ);
+                        if (seen.add(neighbourKey)) {
+                            queue.enqueue(neighbourKey);
+                        }
+                    }
+                }
+            }
+
+            final Optional<PoiSection> poiSectionOptional = load ? poiStorage.getOrLoad(key) : poiStorage.get(key);
+
+            if (poiSectionOptional == null || !poiSectionOptional.isPresent()) {
+                continue;
+            }
+
+            final PoiSection poiSection = poiSectionOptional.orElse(null);
+
+            final Map<Holder<PoiType>, Set<PoiRecord>> sectionData = poiSection.getData();
+            if (sectionData.isEmpty()) {
+                continue;
+            }
+
+            // now we search the section data
+            for (final Map.Entry<Holder<PoiType>, Set<PoiRecord>> entry : sectionData.entrySet()) {
+                if (!villagePlaceType.test(entry.getKey())) {
+                    // filter out by poi type
+                    continue;
+                }
+
+                // now we can look at the poi data
+                for (final PoiRecord poiData : entry.getValue()) {
+                    if (!occupancyFilter.test(poiData)) {
+                        // filter by occupancy
+                        continue;
+                    }
+
+                    final BlockPos poiPosition = poiData.getPos();
+
+                    if (Math.abs(poiPosition.getX() - sourcePosition.getX()) > range
+                            || Math.abs(poiPosition.getZ() - sourcePosition.getZ()) > range) {
+                        // out of range for square radius
+                        continue;
+                    }
+
+                    // it's important that it's poiPosition.distSqr(source) : the value actually is different IF the values are swapped!
+                    final double dataRange = poiPosition.distSqr(sourcePosition);
+
+                    if (dataRange > maxDistanceSquared) {
+                        // out of range for distance check
+                        continue;
+                    }
+
+                    if (dataRange > furthestDistanceSquared && totalRecords >= max) {
+                        // out of range for distance check
+                        continue;
+                    }
+
+                    if (positionPredicate != null && !positionPredicate.test(poiPosition)) {
+                        // filter by position
+                        continue;
+                    }
+
+                    if (dataRange > furthestDistanceSquared) {
+                        // we know totalRecords < max, so this entry is now our furthest
+                        furthestDistanceSquared = dataRange;
+                    }
+
+                    closestRecords.computeIfAbsent(dataRange, (final double unused) -> {
+                        return new ArrayList<>();
+                    }).add(poiData);
+
+                    if (++totalRecords >= max) {
+                        if (closestRecords.size() >= 2) {
+                            int entriesInClosest = 0;
+                            final Iterator<Double2ObjectMap.Entry<List<PoiRecord>>> iterator = closestRecords.double2ObjectEntrySet().iterator();
+                            double nextFurthestDistanceSquared = 0.0;
+
+                            for (int i = 0, len = closestRecords.size() - 1; i < len; ++i) {
+                                final Double2ObjectMap.Entry<List<PoiRecord>> recordEntry = iterator.next();
+                                entriesInClosest += recordEntry.getValue().size();
+                                nextFurthestDistanceSquared = recordEntry.getDoubleKey();
+                            }
+
+                            if (entriesInClosest >= max) {
+                                // the last set of entries at range wont even be considered for sure... nuke em
+                                final Double2ObjectMap.Entry<List<PoiRecord>> recordEntry = iterator.next();
+                                totalRecords -= recordEntry.getValue().size();
+                                iterator.remove();
+
+                                furthestDistanceSquared = nextFurthestDistanceSquared;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        final List<PoiRecord> closestRecordsUnsorted = new ArrayList<>();
+
+        // we're done here, so now just flatten the map and sort it.
+
+        for (final List<PoiRecord> records : closestRecords.values()) {
+            closestRecordsUnsorted.addAll(records);
+        }
+
+        // uh oh! we might have multiple records that match the distance sorting!
+        // we need to re-order our results by the way vanilla would have iterated over them.
+        closestRecordsUnsorted.sort((record1, record2) -> {
+            // vanilla iterates the same way we do for data inside sections, so we know the ordering inside a section
+            // is fine and should be preserved (this sort is stable so we're good there)
+            // but they iterate sections by x then by z (like the following)
+            // for (int x = -dx; x <= dx; ++x)
+            //     for (int z = -dz; z <= dz; ++z)
+            //  ....
+            // so we need to reorder such that records with lower chunk z, then lower chunk x come first
+            final BlockPos pos1 = record1.getPos();
+            final BlockPos pos2 = record2.getPos();
+
+            final int cx1 = pos1.getX() >> 4;
+            final int cz1 = pos1.getZ() >> 4;
+
+            final int cx2 = pos2.getX() >> 4;
+            final int cz2 = pos2.getZ() >> 4;
+
+            if (cz2 != cz1) {
+                // want smaller z
+                return Integer.compare(cz1, cz2);
+            }
+
+            if (cx2 != cx1) {
+                // want smaller x
+                return Integer.compare(cx1, cx2);
+            }
+
+            // same chunk
+            // once vanilla has the chunk, it will iterate from all of the chunk sections starting from smaller y
+            // so now we just compare section y, wanting smaller section y
+
+            return Integer.compare(pos1.getY() >> 4, pos2.getY() >> 4);
+        });
+
+        // trim out any entries exceeding our maximum
+        for (int i = closestRecordsUnsorted.size() - 1; i >= max; --i) {
+            closestRecordsUnsorted.remove(i);
+        }
+
+        // now we match perfectly what vanilla would have outputted, without having to search the whole radius (hopefully).
+        ret.addAll(closestRecordsUnsorted);
+    }
+
+    public static BlockPos findAnyPoiPosition(final PoiManager poiStorage,
+                                              final Predicate<Holder<PoiType>> villagePlaceType,
+                                              final Predicate<BlockPos> positionPredicate,
+                                              final BlockPos sourcePosition,
+                                              final int range, // distance on x y z axis
+                                              final PoiManager.Occupancy occupancy,
+                                              final boolean load) {
+        final PoiRecord ret = findAnyPoiRecord(
+                poiStorage, villagePlaceType, positionPredicate, sourcePosition, range, occupancy, load
+        );
+
+        return ret == null ? null : ret.getPos();
+    }
+
+    public static void findAnyPoiPositions(final PoiManager poiStorage,
+                                           final Predicate<Holder<PoiType>> villagePlaceType,
+                                           final Predicate<BlockPos> positionPredicate,
+                                           final BlockPos sourcePosition,
+                                           final int range, // distance on x y z axis
+                                           final PoiManager.Occupancy occupancy,
+                                           final boolean load,
+                                           final int max,
+                                           final List<Pair<Holder<PoiType>, BlockPos>> ret) {
+        final Set<BlockPos> positions = new HashSet<>();
+        // pos predicate is last thing that runs before adding to ret.
+        final Predicate<BlockPos> newPredicate = (final BlockPos pos) -> {
+            if (positionPredicate != null && !positionPredicate.test(pos)) {
+                return false;
+            }
+            return positions.add(pos.immutable());
+        };
+
+        final List<PoiRecord> toConvert = new ArrayList<>();
+        findAnyPoiRecords(
+                poiStorage, villagePlaceType, newPredicate, sourcePosition, range, occupancy, load, max, toConvert
+        );
+
+        for (final PoiRecord record : toConvert) {
+            ret.add(Pair.of(record.getPoiType(), record.getPos()));
+        }
+    }
+
+    public static PoiRecord findAnyPoiRecord(final PoiManager poiStorage,
+                                             final Predicate<Holder<PoiType>> villagePlaceType,
+                                             final Predicate<BlockPos> positionPredicate,
+                                             final BlockPos sourcePosition,
+                                             final int range, // distance on x y z axis
+                                             final PoiManager.Occupancy occupancy,
+                                             final boolean load) {
+        final List<PoiRecord> ret = new ArrayList<>();
+        findAnyPoiRecords(poiStorage, villagePlaceType, positionPredicate, sourcePosition, range, occupancy, load, 1, ret);
+        return ret.isEmpty() ? null : ret.get(0);
+    }
+
+    public static void findAnyPoiRecords(final PoiManager poiStorage,
+                                         final Predicate<Holder<PoiType>> villagePlaceType,
+                                         final Predicate<BlockPos> positionPredicate,
+                                         final BlockPos sourcePosition,
+                                         final int range, // distance on x y z axis
+                                         final PoiManager.Occupancy occupancy,
+                                         final boolean load,
+                                         final int max,
+                                         final List<PoiRecord> ret) {
+        // the biggest issue with the original mojang implementation is that they chain so many streams together
+        // the amount of streams chained just rolls performance, even if nothing is iterated over
+        final Predicate<? super PoiRecord> occupancyFilter = occupancy.getTest();
+        final double rangeSquared = range * range;
+
+        int added = 0;
+
+        // First up, we need to iterate the chunks
+        // all the values here are in chunk sections
+        final int lowerX = Mth.floor(sourcePosition.getX() - range) >> 4;
+        final int lowerY = Math.max(WorldUtil.getMinSection(poiStorage.world), Mth.floor(sourcePosition.getY() - range) >> 4);
+        final int lowerZ = Mth.floor(sourcePosition.getZ() - range) >> 4;
+        final int upperX = Mth.floor(sourcePosition.getX() + range) >> 4;
+        final int upperY = Math.min(WorldUtil.getMaxSection(poiStorage.world), Mth.floor(sourcePosition.getY() + range) >> 4);
+        final int upperZ = Mth.floor(sourcePosition.getZ() + range) >> 4;
+
+        // Vanilla iterates by x until max is reached then increases z
+        // vanilla also searches by increasing Y section value
+        for (int currZ = lowerZ; currZ <= upperZ; ++currZ) {
+            for (int currX = lowerX; currX <= upperX; ++currX) {
+                for (int currY = lowerY; currY <= upperY; ++currY) { // vanilla searches the entire chunk because they're actually stupid. just search the sections we need
+                    final Optional<PoiSection> poiSectionOptional = load ? poiStorage.getOrLoad(CoordinateUtils.getChunkSectionKey(currX, currY, currZ)) :
+                            poiStorage.get(CoordinateUtils.getChunkSectionKey(currX, currY, currZ));
+                    final PoiSection poiSection = poiSectionOptional == null ? null : poiSectionOptional.orElse(null);
+                    if (poiSection == null) {
+                        continue;
+                    }
+
+                    final Map<Holder<PoiType>, Set<PoiRecord>> sectionData = poiSection.getData();
+                    if (sectionData.isEmpty()) {
+                        continue;
+                    }
+
+                    // now we search the section data
+                    for (final Map.Entry<Holder<PoiType>, Set<PoiRecord>> entry : sectionData.entrySet()) {
+                        if (!villagePlaceType.test(entry.getKey())) {
+                            // filter out by poi type
+                            continue;
+                        }
+
+                        // now we can look at the poi data
+                        for (final PoiRecord poiData : entry.getValue()) {
+                            if (!occupancyFilter.test(poiData)) {
+                                // filter by occupancy
+                                continue;
+                            }
+
+                            final BlockPos poiPosition = poiData.getPos();
+
+                            if (Math.abs(poiPosition.getX() - sourcePosition.getX()) > range
+                                    || Math.abs(poiPosition.getZ() - sourcePosition.getZ()) > range) {
+                                // out of range for square radius
+                                continue;
+                            }
+
+                            if (poiPosition.distSqr(sourcePosition) > rangeSquared) {
+                                // out of range for distance check
+                                continue;
+                            }
+
+                            if (positionPredicate != null && !positionPredicate.test(poiPosition)) {
+                                // filter by position
+                                continue;
+                            }
+
+                            // found one!
+                            ret.add(poiData);
+                            if (++added >= max) {
+                                return;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    private PoiAccess() {
+        throw new RuntimeException();
+    }
+}
diff --git a/src/main/java/net/minecraft/world/entity/ai/behavior/AcquirePoi.java b/src/main/java/net/minecraft/world/entity/ai/behavior/AcquirePoi.java
index 4f75f2be7070d49c2c60866ad7146da19ab61652..43243537b765a2d270be6de3f053fea77ff67d18 100644
--- a/src/main/java/net/minecraft/world/entity/ai/behavior/AcquirePoi.java
+++ b/src/main/java/net/minecraft/world/entity/ai/behavior/AcquirePoi.java
@@ -87,7 +87,11 @@ public class AcquirePoi extends Behavior<PathfinderMob> {
                 return true;
             }
         };
-        Set<Pair<Holder<PoiType>, BlockPos>> set = poiManager.findAllClosestFirstWithType(this.poiType, predicate, entity.blockPosition(), 48, PoiManager.Occupancy.HAS_SPACE).limit(5L).collect(Collectors.toSet());
+        // Paper start - optimise POI access
+        java.util.List<Pair<Holder<PoiType>, BlockPos>> poiposes = new java.util.ArrayList<>();
+        io.papermc.paper.util.PoiAccess.findNearestPoiPositions(poiManager, this.poiType, predicate, entity.blockPosition(), 48, 48*48, PoiManager.Occupancy.HAS_SPACE, false, 5, poiposes);
+        Set<Pair<Holder<PoiType>, BlockPos>> set = new java.util.HashSet<>(poiposes);
+        // Paper end - optimise POI access
         Path path = findPathToPois(entity, set);
         if (path != null && path.canReach()) {
             BlockPos blockPos = path.getTarget();
diff --git a/src/main/java/net/minecraft/world/entity/ai/sensing/NearestBedSensor.java b/src/main/java/net/minecraft/world/entity/ai/sensing/NearestBedSensor.java
index 33fbf72b440e0d164ecd4fb0fdec72e2394d0a1e..8db20db72cd51046213625fac46c35854c59ec5d 100644
--- a/src/main/java/net/minecraft/world/entity/ai/sensing/NearestBedSensor.java
+++ b/src/main/java/net/minecraft/world/entity/ai/sensing/NearestBedSensor.java
@@ -53,10 +53,12 @@ public class NearestBedSensor extends Sensor<Mob> {
                     return true;
                 }
             };
-            Set<Pair<Holder<PoiType>, BlockPos>> set = poiManager.findAllWithType((holder) -> {
-                return holder.is(PoiTypes.HOME);
-            }, predicate, entity.blockPosition(), 48, PoiManager.Occupancy.ANY).collect(Collectors.toSet());
-            Path path = AcquirePoi.findPathToPois(entity, set);
+            // Paper start - optimise POI access
+            java.util.List<Pair<Holder<PoiType>, BlockPos>> poiposes = new java.util.ArrayList<>();
+            // don't ask me why it's unbounded. ask mojang.
+            io.papermc.paper.util.PoiAccess.findAnyPoiPositions(poiManager, type -> type.is(PoiTypes.HOME), predicate, entity.blockPosition(), 48, PoiManager.Occupancy.ANY, false, Integer.MAX_VALUE, poiposes);
+            Path path = AcquirePoi.findPathToPois(entity, new java.util.HashSet<>(poiposes));
+            // Paper end - optimise POI access
             if (path != null && path.canReach()) {
                 BlockPos blockPos = path.getTarget();
                 Optional<Holder<PoiType>> optional = poiManager.getType(blockPos);
diff --git a/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiManager.java b/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiManager.java
index 8938e04ffab2d31e64b80879d21d9f1eb90c20bb..fea4dd3fe06e66f72969331fdf9491dbbe44f3c2 100644
--- a/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiManager.java
+++ b/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiManager.java
@@ -127,43 +127,62 @@ public class PoiManager extends SectionStorage<PoiSection> {
     }
 
     public Optional<BlockPos> find(Predicate<Holder<PoiType>> typePredicate, Predicate<BlockPos> posPredicate, BlockPos pos, int radius, PoiManager.Occupancy occupationStatus) {
-        return this.findAll(typePredicate, posPredicate, pos, radius, occupationStatus).findFirst();
+        // Paper start - re-route to faster logic
+        BlockPos ret = io.papermc.paper.util.PoiAccess.findAnyPoiPosition(this, typePredicate, posPredicate, pos, radius, occupationStatus, false);
+        return Optional.ofNullable(ret);
+        // Paper end
     }
 
     public Optional<BlockPos> findClosest(Predicate<Holder<PoiType>> typePredicate, BlockPos pos, int radius, PoiManager.Occupancy occupationStatus) {
-        return this.getInRange(typePredicate, pos, radius, occupationStatus).map(PoiRecord::getPos).min(Comparator.comparingDouble((blockPos2) -> {
-            return blockPos2.distSqr(pos);
-        }));
+        // Paper start - re-route to faster logic
+        BlockPos ret = io.papermc.paper.util.PoiAccess.findClosestPoiDataPosition(this, typePredicate, null, pos, radius, radius * radius, occupationStatus, false);
+        return Optional.ofNullable(ret);
+        // Paper end - re-route to faster logic
     }
 
     public Optional<Pair<Holder<PoiType>, BlockPos>> findClosestWithType(Predicate<Holder<PoiType>> typePredicate, BlockPos pos, int radius, PoiManager.Occupancy occupationStatus) {
-        return this.getInRange(typePredicate, pos, radius, occupationStatus).min(Comparator.comparingDouble((poi) -> {
-            return poi.getPos().distSqr(pos);
-        })).map((poi) -> {
-            return Pair.of(poi.getPoiType(), poi.getPos());
-        });
+        // Paper start - re-route to faster logic
+        return Optional.ofNullable(io.papermc.paper.util.PoiAccess.findClosestPoiDataTypeAndPosition(
+            this, typePredicate, null, pos, radius, radius * radius, occupationStatus, false
+        ));
+        // Paper end - re-route to faster logic
     }
 
     public Optional<BlockPos> findClosest(Predicate<Holder<PoiType>> typePredicate, Predicate<BlockPos> posPredicate, BlockPos pos, int radius, PoiManager.Occupancy occupationStatus) {
-        return this.getInRange(typePredicate, pos, radius, occupationStatus).map(PoiRecord::getPos).filter(posPredicate).min(Comparator.comparingDouble((blockPos2) -> {
-            return blockPos2.distSqr(pos);
-        }));
+        // Paper start - re-route to faster logic
+        BlockPos ret = io.papermc.paper.util.PoiAccess.findClosestPoiDataPosition(this, typePredicate, posPredicate, pos, radius, radius * radius, occupationStatus, false);
+        return Optional.ofNullable(ret);
+        // Paper end - re-route to faster logic
     }
 
     public Optional<BlockPos> take(Predicate<Holder<PoiType>> typePredicate, BiPredicate<Holder<PoiType>, BlockPos> biPredicate, BlockPos pos, int radius) {
-        return this.getInRange(typePredicate, pos, radius, PoiManager.Occupancy.HAS_SPACE).filter((poi) -> {
-            return biPredicate.test(poi.getPoiType(), poi.getPos());
-        }).findFirst().map((poi) -> {
+        // Paper start - re-route to faster logic
+        final @javax.annotation.Nullable PoiRecord closest = io.papermc.paper.util.PoiAccess.findClosestPoiDataRecord(
+            this, typePredicate, biPredicate, pos, radius, radius * radius, Occupancy.HAS_SPACE, false
+        );
+        return Optional.ofNullable(closest).map(poi -> {
+            // Paper end - re-route to faster logic
             poi.acquireTicket();
             return poi.getPos();
         });
     }
 
     public Optional<BlockPos> getRandom(Predicate<Holder<PoiType>> typePredicate, Predicate<BlockPos> positionPredicate, PoiManager.Occupancy occupationStatus, BlockPos pos, int radius, RandomSource random) {
-        List<PoiRecord> list = Util.toShuffledList(this.getInRange(typePredicate, pos, radius, occupationStatus), random);
-        return list.stream().filter((poi) -> {
-            return positionPredicate.test(poi.getPos());
-        }).findFirst().map(PoiRecord::getPos);
+        // Paper start - re-route to faster logic
+        List<PoiRecord> list = new java.util.ArrayList<>();
+        io.papermc.paper.util.PoiAccess.findAnyPoiRecords(
+            this, typePredicate, positionPredicate, pos, radius, occupationStatus, false, Integer.MAX_VALUE, list
+        );
+
+        // the old method shuffled the list and then tried to find the first element in it that
+        // matched positionPredicate, however we moved positionPredicate into the poi search. This means we can avoid a
+        // shuffle entirely, and just pick a random element from list
+        if (list.isEmpty()) {
+            return Optional.empty();
+        }
+
+        return Optional.of(list.get(random.nextInt(list.size())).getPos());
+        // Paper end - re-route to faster logic
     }
 
     public boolean release(BlockPos pos) {
diff --git a/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiSection.java b/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiSection.java
index d0ce7b14d29459e276961c38cfc5b5da1cd15634..2e410b21564a067ed04f4179908fba8389062f4c 100644
--- a/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiSection.java
+++ b/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiSection.java
@@ -26,7 +26,7 @@ import org.slf4j.Logger;
 public class PoiSection {
     private static final Logger LOGGER = LogUtils.getLogger();
     private final Short2ObjectMap<PoiRecord> records = new Short2ObjectOpenHashMap<>();
-    private final Map<Holder<PoiType>, Set<PoiRecord>> byType = Maps.newHashMap();
+    private final Map<Holder<PoiType>, Set<PoiRecord>> byType = Maps.newHashMap(); public final Map<Holder<PoiType>, Set<PoiRecord>> getData() { return this.byType; } // Paper - public accessor
     private final Runnable setDirty;
     private boolean isValid;
     public final Optional<PoiSection> noAllocateOptional = Optional.of(this); // Paper - rewrite chunk system
diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/SectionStorage.java b/src/main/java/net/minecraft/world/level/chunk/storage/SectionStorage.java
index c886d461304ad19483eb92a25f5827a95b8cba98..1a0095b9dee1f708c4c3d32fd95b88120245f1e9 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/SectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/SectionStorage.java
@@ -71,11 +71,11 @@ public class SectionStorage<R> extends RegionFileStorage implements AutoCloseabl
     }
 
     @Nullable
-    protected Optional<R> get(long pos) {
+    public Optional<R> get(long pos) { // Paper - public
         return this.storage.get(pos);
     }
 
-    protected Optional<R> getOrLoad(long pos) {
+    public Optional<R> getOrLoad(long pos) { // Paper - public
         if (this.outsideStoredRange(pos)) {
             return Optional.empty();
         } else {
diff --git a/src/main/java/net/minecraft/world/level/portal/PortalForcer.java b/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
index 1311d69bb2fa7b3617936e6ad6eb5236fedc260d..386a73f32f2504af81107852307dcd393d4d8a11 100644
--- a/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
+++ b/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
@@ -51,18 +51,39 @@ public class PortalForcer {
         // int i = flag ? 16 : 128;
         // CraftBukkit end
 
-        villageplace.ensureLoadedAndValid(this.level, blockposition, i);
-        Optional<PoiRecord> optional = villageplace.getInSquare((holder) -> {
-            return holder.is(PoiTypes.NETHER_PORTAL);
-        }, blockposition, i, PoiManager.Occupancy.ANY).filter((villageplacerecord) -> {
-            return worldborder.isWithinBounds(villageplacerecord.getPos());
-        }).sorted(Comparator.comparingDouble((PoiRecord villageplacerecord) -> { // CraftBukkit - decompile error
-            return villageplacerecord.getPos().distSqr(blockposition);
-        }).thenComparingInt((villageplacerecord) -> {
-            return villageplacerecord.getPos().getY();
-        })).filter((villageplacerecord) -> {
-            return this.level.getBlockState(villageplacerecord.getPos()).hasProperty(BlockStateProperties.HORIZONTAL_AXIS);
-        }).findFirst();
+        // Paper start - optimise portals
+        Optional<PoiRecord> optional;
+        java.util.List<PoiRecord> records = new java.util.ArrayList<>();
+        io.papermc.paper.util.PoiAccess.findClosestPoiDataRecords(
+            villageplace,
+            type -> type.is(PoiTypes.NETHER_PORTAL),
+            (BlockPos pos) -> {
+                net.minecraft.world.level.chunk.ChunkAccess lowest = this.level.getChunk(pos.getX() >> 4, pos.getZ() >> 4, net.minecraft.world.level.chunk.ChunkStatus.EMPTY);
+                if (!lowest.getStatus().isOrAfter(net.minecraft.world.level.chunk.ChunkStatus.FULL)
+                    && (lowest.getBelowZeroRetrogen() == null || !lowest.getBelowZeroRetrogen().targetStatus().isOrAfter(net.minecraft.world.level.chunk.ChunkStatus.HEIGHTMAPS))) {
+                    // why would we generate the chunk?
+                    return false;
+                }
+                if (!worldborder.isWithinBounds(pos)) {
+                    return false;
+                }
+                return lowest.getBlockState(pos).hasProperty(BlockStateProperties.HORIZONTAL_AXIS);
+            },
+            blockposition, i, Double.MAX_VALUE, PoiManager.Occupancy.ANY, true, records
+        );
+
+        // this gets us most of the way there, but we bias towards lower y values.
+        PoiRecord lowestYRecord = null;
+        for (PoiRecord record : records) {
+            if (lowestYRecord == null) {
+                lowestYRecord = record;
+            } else if (lowestYRecord.getPos().getY() > record.getPos().getY()) {
+                lowestYRecord = record;
+            }
+        }
+        // now we're done
+        optional = Optional.ofNullable(lowestYRecord);
+        // Paper end - optimise portals
 
         return optional.map((villageplacerecord) -> {
             BlockPos blockposition1 = villageplacerecord.getPos();