Revert "apacheGH-343: Fix BaseVariableWidthVector and BaseLargeVariableWidthVector offset buffer serialization (apache#989)"

This reverts commit 77df3ec.

Author: lriggs

adapter/jdbc/src/test/java/org/apache/arrow/adapter/jdbc/ResultSetUtilityTest.java

@@ -43,19 +43,15 @@ public void testZeroRowResultSet() throws Exception {
                 .setReuseVectorSchemaRoot(reuseVectorSchemaRoot)
                 .build();
 
-        try (ArrowVectorIterator iter = JdbcToArrow.sqlToArrowVectorIterator(rs, config)) {
-          assertTrue(iter.hasNext(), "Iterator on zero row ResultSet should haveNext() before use");
-          VectorSchemaRoot root = iter.next();
-          assertNotNull(root, "VectorSchemaRoot from first next() result should never be null");
-          assertEquals(
-              0, root.getRowCount(), "VectorSchemaRoot from empty ResultSet should have zero rows");
-          assertFalse(
-              iter.hasNext(),
-              "hasNext() should return false on empty ResultSets after initial next() call");
-          if (!reuseVectorSchemaRoot) {
-            root.close();
-          }
-        }
+        ArrowVectorIterator iter = JdbcToArrow.sqlToArrowVectorIterator(rs, config);
+        assertTrue(iter.hasNext(), "Iterator on zero row ResultSet should haveNext() before use");
+        VectorSchemaRoot root = iter.next();
+        assertNotNull(root, "VectorSchemaRoot from first next() result should never be null");
+        assertEquals(
+            0, root.getRowCount(), "VectorSchemaRoot from empty ResultSet should have zero rows");
+        assertFalse(
+            iter.hasNext(),
+            "hasNext() should return false on empty ResultSets after initial next() call");
       }
     }
   }

vector/src/main/java/org/apache/arrow/vector/BaseLargeVariableWidthVector.java

@@ -373,26 +373,14 @@ private void setReaderAndWriterIndex() {
     valueBuffer.readerIndex(0);
     if (valueCount == 0) {
       validityBuffer.writerIndex(0);
+      offsetBuffer.writerIndex(0);
       valueBuffer.writerIndex(0);
     } else {
       final long lastDataOffset = getStartOffset(valueCount);
       validityBuffer.writerIndex(BitVectorHelper.getValidityBufferSizeFromCount(valueCount));
+      offsetBuffer.writerIndex((long) (valueCount + 1) * OFFSET_WIDTH);
       valueBuffer.writerIndex(lastDataOffset);
     }
-    // IPC serializer will determine readable bytes based on `readerIndex` and `writerIndex`.
-    // Both are set to 0 means 0 bytes are written to the IPC stream which will crash IPC readers
-    // in other libraries. According to Arrow spec, we should still output the offset buffer which
-    // is [0].
-    final long requiredOffsetBufferSize = (long) (valueCount + 1) * OFFSET_WIDTH;
-    if (offsetBuffer.capacity() < requiredOffsetBufferSize) {
-      ArrowBuf newOffsetBuffer = allocateOffsetBuffer(requiredOffsetBufferSize);
-      if (offsetBuffer.capacity() > 0) {
-        newOffsetBuffer.setBytes(0, offsetBuffer, 0, offsetBuffer.capacity());
-      }
-      offsetBuffer.getReferenceManager().release();
-      offsetBuffer = newOffsetBuffer;
-    }
-    offsetBuffer.writerIndex(requiredOffsetBufferSize);
   }
 
   /** Same as {@link #allocateNewSafe()}. */

vector/src/main/java/org/apache/arrow/vector/BaseVariableWidthVector.java

@@ -389,26 +389,14 @@ private void setReaderAndWriterIndex() {
     valueBuffer.readerIndex(0);
     if (valueCount == 0) {
       validityBuffer.writerIndex(0);
+      offsetBuffer.writerIndex(0);
       valueBuffer.writerIndex(0);
     } else {
       final int lastDataOffset = getStartOffset(valueCount);
       validityBuffer.writerIndex(BitVectorHelper.getValidityBufferSizeFromCount(valueCount));
+      offsetBuffer.writerIndex((long) (valueCount + 1) * OFFSET_WIDTH);
       valueBuffer.writerIndex(lastDataOffset);
     }
-    // IPC serializer will determine readable bytes based on `readerIndex` and `writerIndex`.
-    // Both are set to 0 means 0 bytes are written to the IPC stream which will crash IPC readers
-    // in other libraries. According to Arrow spec, we should still output the offset buffer which
-    // is [0].
-    final long requiredOffsetBufferSize = (long) (valueCount + 1) * OFFSET_WIDTH;
-    if (offsetBuffer.capacity() < requiredOffsetBufferSize) {
-      ArrowBuf newOffsetBuffer = allocateOffsetBuffer(requiredOffsetBufferSize);
-      if (offsetBuffer.capacity() > 0) {
-        newOffsetBuffer.setBytes(0, offsetBuffer, 0, offsetBuffer.capacity());
-      }
-      offsetBuffer.getReferenceManager().release();
-      offsetBuffer = newOffsetBuffer;
-    }
-    offsetBuffer.writerIndex(requiredOffsetBufferSize);
   }
 
   /** Same as {@link #allocateNewSafe()}. */

vector/src/test/java/org/apache/arrow/vector/TestValueVector.java

@@ -3940,42 +3940,4 @@ public void testVectorLoadUnloadOnNonVariadicVectors() {
       }
     }
   }
-
-  @Test
-  public void testEmptyVarCharOffsetBuffer() {
-    // Validates that offset buffer has at least OFFSET_WIDTH bytes (for offset[0]=0)
-    // even when valueCount is 0, per Arrow specification.
-    try (VarCharVector vector = newVarCharVector("varchar", allocator)) {
-      vector.allocateNew();
-      vector.setValueCount(0);
-
-      List<ArrowBuf> buffers = vector.getFieldBuffers();
-      // buffers: [validity, offset, data]
-      assertTrue(
-          buffers.get(1).readableBytes() >= BaseVariableWidthVector.OFFSET_WIDTH,
-          "Offset buffer should have at least "
-              + BaseVariableWidthVector.OFFSET_WIDTH
-              + " bytes for offset[0]");
-      assertEquals(0, vector.getOffsetBuffer().getInt(0));
-    }
-  }
-
-  @Test
-  public void testEmptyLargeVarCharOffsetBuffer() {
-    // Validates that offset buffer has at least OFFSET_WIDTH bytes (for offset[0]=0)
-    // even when valueCount is 0, per Arrow specification.
-    try (LargeVarCharVector vector = new LargeVarCharVector("largevarchar", allocator)) {
-      vector.allocateNew();
-      vector.setValueCount(0);
-
-      List<ArrowBuf> buffers = vector.getFieldBuffers();
-      // buffers: [validity, offset, data]
-      assertTrue(
-          buffers.get(1).readableBytes() >= BaseLargeVariableWidthVector.OFFSET_WIDTH,
-          "Offset buffer should have at least "
-              + BaseLargeVariableWidthVector.OFFSET_WIDTH
-              + " bytes for offset[0]");
-      assertEquals(0, vector.getOffsetBuffer().getLong(0));
-    }
-  }
 }