Use little-endian for QWP decimal wire format

QWP transmitted DECIMAL64/128/256 values in big-endian while all
other numeric types used little-endian. This was inherited from
Parquet's convention but served no purpose in QWP, which is its
own protocol.

Switch decimal columns to little-endian on the wire, matching
Cairo's in-memory layout. This replaces putLongBE() with
putLong() in QwpColumnWriter and deletes the now-unused
putLongBE() method from the buffer writer interface and its
implementations.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mtopolnik

core/src/main/java/io/questdb/client/cutlass/http/client/WebSocketSendBuffer.java

@@ -310,15 +310,6 @@ public void putLong(long value) {
         writePos += 8;
     }
 
-    /**
-     * Writes a long value in big-endian format.
-     */
-    public void putLongBE(long value) {
-        ensureCapacity(8);
-        Unsafe.getUnsafe().putLong(bufPtr + writePos, Long.reverseBytes(value));
-        writePos += 8;
-    }
-
     /**
      * Writes a short value in little-endian format.
      */

core/src/main/java/io/questdb/client/cutlass/qwp/client/NativeBufferWriter.java

@@ -211,16 +211,6 @@ public void putLong(long value) {
         position += 8;
     }
 
-    /**
-     * Writes a long in big-endian order.
-     */
-    @Override
-    public void putLongBE(long value) {
-        ensureCapacity(8);
-        Unsafe.getUnsafe().putLong(bufferPtr + position, Long.reverseBytes(value));
-        position += 8;
-    }
-
     /**
      * Writes a short (2 bytes, little-endian).
      */

core/src/main/java/io/questdb/client/cutlass/qwp/client/QwpBufferWriter.java

@@ -39,8 +39,7 @@
  *   <li>{@link io.questdb.client.cutlass.http.client.WebSocketSendBuffer} - WebSocket frame buffer</li>
  * </ul>
  * <p>
- * All multi-byte values are written in little-endian format unless the method
- * name explicitly indicates big-endian (e.g., {@link #putLongBE}).
+ * All multi-byte values are written in little-endian format.
  */
 public interface QwpBufferWriter extends ArrayBufferAppender {
 
@@ -85,11 +84,6 @@ public interface QwpBufferWriter extends ArrayBufferAppender {
      */
     void putFloat(float value);
 
-    /**
-     * Writes a long in big-endian byte order.
-     */
-    void putLongBE(long value);
-
     /**
      * Writes a short (2 bytes, little-endian).
      */

core/src/main/java/io/questdb/client/cutlass/qwp/client/QwpColumnWriter.java

@@ -194,26 +194,26 @@ private void writeDecimal128Column(byte scale, long addr, int count) {
             long offset = (long) i * 16;
             long hi = Unsafe.getUnsafe().getLong(addr + offset);
             long lo = Unsafe.getUnsafe().getLong(addr + offset + 8);
-            buffer.putLongBE(hi);
-            buffer.putLongBE(lo);
+            buffer.putLong(hi);
+            buffer.putLong(lo);
         }
     }
 
     private void writeDecimal256Column(byte scale, long addr, int count) {
         buffer.putByte(scale);
         for (int i = 0; i < count; i++) {
             long offset = (long) i * 32;
-            buffer.putLongBE(Unsafe.getUnsafe().getLong(addr + offset));
-            buffer.putLongBE(Unsafe.getUnsafe().getLong(addr + offset + 8));
-            buffer.putLongBE(Unsafe.getUnsafe().getLong(addr + offset + 16));
-            buffer.putLongBE(Unsafe.getUnsafe().getLong(addr + offset + 24));
+            buffer.putLong(Unsafe.getUnsafe().getLong(addr + offset));
+            buffer.putLong(Unsafe.getUnsafe().getLong(addr + offset + 8));
+            buffer.putLong(Unsafe.getUnsafe().getLong(addr + offset + 16));
+            buffer.putLong(Unsafe.getUnsafe().getLong(addr + offset + 24));
         }
     }
 
     private void writeDecimal64Column(byte scale, long addr, int count) {
         buffer.putByte(scale);
         for (int i = 0; i < count; i++) {
-            buffer.putLongBE(Unsafe.getUnsafe().getLong(addr + (long) i * 8));
+            buffer.putLong(Unsafe.getUnsafe().getLong(addr + (long) i * 8));
         }
     }
 

core/src/main/java/io/questdb/client/cutlass/qwp/client/SegmentedNativeBufferWriter.java

@@ -116,11 +116,6 @@ public void putLong(long value) {
         currentChunk.putLong(value);
     }
 
-    @Override
-    public void putLongBE(long value) {
-        currentChunk.putLongBE(value);
-    }
-
     @Override
     public void putShort(short value) {
         currentChunk.putShort(value);

core/src/test/java/io/questdb/client/test/cutlass/qwp/client/NativeBufferWriterTest.java

@@ -379,26 +379,6 @@ public void testWriteLong() throws Exception {
         });
     }
 
-    @Test
-    public void testWriteLongBigEndian() throws Exception {
-        assertMemoryLeak(() -> {
-            try (NativeBufferWriter writer = new NativeBufferWriter()) {
-                writer.putLongBE(0x0102030405060708L);
-                Assert.assertEquals(8, writer.getPosition());
-                // Check big-endian byte order
-                long ptr = writer.getBufferPtr();
-                Assert.assertEquals((byte) 0x01, Unsafe.getUnsafe().getByte(ptr));
-                Assert.assertEquals((byte) 0x02, Unsafe.getUnsafe().getByte(ptr + 1));
-                Assert.assertEquals((byte) 0x03, Unsafe.getUnsafe().getByte(ptr + 2));
-                Assert.assertEquals((byte) 0x04, Unsafe.getUnsafe().getByte(ptr + 3));
-                Assert.assertEquals((byte) 0x05, Unsafe.getUnsafe().getByte(ptr + 4));
-                Assert.assertEquals((byte) 0x06, Unsafe.getUnsafe().getByte(ptr + 5));
-                Assert.assertEquals((byte) 0x07, Unsafe.getUnsafe().getByte(ptr + 6));
-                Assert.assertEquals((byte) 0x08, Unsafe.getUnsafe().getByte(ptr + 7));
-            }
-        });
-    }
-
     @Test
     public void testWriteNullString() throws Exception {
         assertMemoryLeak(() -> {