Review fixes

Author: JonasKunz

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/data/ExponentialHistogramArrayBlock.java

@@ -204,15 +204,14 @@ private BlockBackedHistogram(BytesRef bytes) {
         }
 
         static BytesRef encode(ExponentialHistogram histogram, BytesRef growableBuffer) {
+            assert growableBuffer.offset == 0;
+
             int totalSize = 1;
 
             resizeIfRequired(growableBuffer, totalSize);
-            BytesRef result = new BytesRef();
-            result.bytes = growableBuffer.bytes;
-            result.offset = growableBuffer.offset;
-            result.length = totalSize;
+            BytesRef result = new BytesRef(growableBuffer.bytes, 0, totalSize);
 
-            ByteBuffer buffer = ByteBuffer.wrap(result.bytes, result.offset, result.length).order(ByteOrder.LITTLE_ENDIAN);
+            ByteBuffer buffer = ByteBuffer.wrap(result.bytes, 0, result.length).order(ByteOrder.LITTLE_ENDIAN);
             buffer.put(SCALE_OFFSET, (byte) histogram.scale());
 
             return result;
@@ -222,7 +221,7 @@ private static void resizeIfRequired(BytesRef growableBuffer, int totalSize) {
             if (growableBuffer.length >= totalSize) {
                 return;
             }
-            growableBuffer.length = Math.max(32, growableBuffer.length);
+            assert growableBuffer.length > 0;
             while (growableBuffer.length < totalSize) {
                 growableBuffer.length *= 2;
             }

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/data/ExponentialHistogramBlockBuilder.java

@@ -14,6 +14,8 @@
 
 public class ExponentialHistogramBlockBuilder implements Block.Builder {
 
+    private static final int INITIAL_SCRATCH_SIZE = 256;
+
     private final BytesRefBlock.Builder encodedHistogramsBuilder;
 
     private final BytesRef tempScratch;
@@ -22,7 +24,7 @@ public class ExponentialHistogramBlockBuilder implements Block.Builder {
 
     ExponentialHistogramBlockBuilder(int estimatedSize, BlockFactory blockFactory) {
         this.encodedHistogramsBuilder = blockFactory.newBytesRefBlockBuilder(estimatedSize);
-        this.tempScratch = new BytesRef(new byte[256], 0, 256);
+        this.tempScratch = new BytesRef(new byte[INITIAL_SCRATCH_SIZE], 0, INITIAL_SCRATCH_SIZE);
     }
 
     public ExponentialHistogramBlockBuilder append(@Nullable ExponentialHistogram value) {