Add dense bulk path for multi-dimensional point fields via BinaryColumn

This commit adds a dense bulk fast path for multi-dimensional point fields
using BinaryColumn. The key optimization is a dynamically-sized dense points
buffer that ensures at least MIN_VALUES_PER_CHUNK (64) values per chunk,
preventing pathologically small chunk sizes for wide point values.

Previously, the N-D dense path used a fixed 4KB shared scratch buffer,
which could result in very small per-chunk counts for high-dimensional
or wide-byte points. The new pointsDenseBuffer() method allocates a
larger buffer when needed to maintain efficient bulk processing.

Also adds comprehensive tests for multi-dimensional point indexing via
BinaryColumn covering LatLonPoint, XYPoint, IntPoint, LongPoint,
FloatPoint, DoublePoint, and InetAddressPoint.

Author: iprithv

lucene/CHANGES.txt

@@ -341,6 +341,7 @@ API Changes
 
 * GITHUB#16224 Add TokenStreamColumn for experimental columnar batch indexing. (Tim Brooks)
 
+* GITHUB#16209: Add dense bulk path for multi-dimensional point fields via BinaryColumn. (Prithvi S)
 
 New Features
 ---------------------

lucene/core/src/java/org/apache/lucene/document/column/BinaryColumn.java

@@ -21,9 +21,9 @@
 import org.apache.lucene.util.BytesRef;
 
 /**
- * A {@link Column} that provides variable-size binary values via a tuple cursor. Used for {@link
- * org.apache.lucene.index.DocValuesType#BINARY BINARY}, {@link
- * org.apache.lucene.index.DocValuesType#SORTED SORTED}, and {@link
+ * A {@link Column} that provides variable-size binary values via a tuple cursor, and dense values
+ * via a {@link BytesRefValuesCursor}. Used for {@link org.apache.lucene.index.DocValuesType#BINARY
+ * BINARY}, {@link org.apache.lucene.index.DocValuesType#SORTED SORTED}, and {@link
  * org.apache.lucene.index.DocValuesType#SORTED_SET SORTED_SET} doc values, and for stored/indexed
  * binary or text fields. Values fed to points are passed through unchanged, so callers are
  * responsible for producing sort-encoded bytes of the correct total length.

lucene/core/src/java/org/apache/lucene/index/PointValuesWriter.java

@@ -58,6 +58,11 @@ class PointValuesWriter {
             + (PointValues.MAX_NUM_BYTES * BKDConfig.MAX_DIMS);
   }
 
+  /** Minimum number of values to process per chunk in the dense N-D bulk path. */
+  private static final int MIN_VALUES_PER_CHUNK = 64;
+
+  private byte[] densePointsBuffer;
+
   PointValuesWriter(Counter bytesUsed, FieldInfo fieldInfo, SharedIndexingScratch sharedScratch) {
     this.fieldInfo = fieldInfo;
     this.iwBytesUsed = bytesUsed;
@@ -137,15 +142,19 @@ void addDense1DLongValues(int firstDocID, LongValuesCursor cursor) throws IOExce
     commitDenseRange(firstDocID, size, ramBefore);
   }
 
+  /**
+   * Bulk-adds dense N-dimensional packed point values from a {@link BytesRefValuesCursor}. Each value
+   * is a pre-encoded packed byte array of {@code packedBytesLength} bytes.
+   */
   void addDenseNDValues(int firstDocID, BytesRefValuesCursor cursor) throws IOException {
     final int size = cursor.size();
     if (size == 0) {
       return;
     }
     final long ramBefore = reserveDenseRange(firstDocID, size);
     final int width = packedBytesLength;
-    final int perChunk = SharedIndexingScratch.BYTES_SCRATCH_SIZE / width;
-    final byte[] buffer = sharedScratch.bytesScratch();
+    final byte[] buffer = pointsDenseBuffer(width);
+    final int perChunk = buffer.length / width;
     int remaining = size;
     while (remaining > 0) {
       int chunk = Math.min(perChunk, remaining);
@@ -156,6 +165,22 @@ void addDenseNDValues(int firstDocID, BytesRefValuesCursor cursor) throws IOExce
     commitDenseRange(firstDocID, size, ramBefore);
   }
 
+  /**
+   * Returns a dense buffer sized to fit at least {@link SharedIndexingScratch#BYTES_SCRATCH_SIZE}
+   * bytes, or a larger buffer if {@code packedLength} requires it to hold at least {@code
+   * MIN_VALUES_PER_CHUNK} values per chunk.
+   */
+  private byte[] pointsDenseBuffer(int packedLength) {
+    final int minBytes = packedLength * MIN_VALUES_PER_CHUNK;
+    if (densePointsBuffer == null) {
+      densePointsBuffer =
+          new byte[Math.max(SharedIndexingScratch.BYTES_SCRATCH_SIZE, minBytes)];
+    } else if (densePointsBuffer.length < minBytes) {
+      densePointsBuffer = new byte[minBytes];
+    }
+    return densePointsBuffer;
+  }
+
   private void validate1DPacked(int byteWidth) {
     if (fieldInfo.getPointDimensionCount() != 1 || fieldInfo.getPointNumBytes() != byteWidth) {
       throw new IllegalArgumentException(