GH-44065: [Java] Implement C Data Interface for RunEndEncodedVector

dev/archery/archery/integration/datagen.py

@@ -1929,7 +1929,6 @@ def _temp_path():
 
         generate_run_end_encoded_case()
         .skip_tester('C#')
-        .skip_tester('Java')
         .skip_tester('JS')
         # TODO(https://github.com/apache/arrow-nanoarrow/issues/618)
         .skip_tester('nanoarrow')

java/c/src/main/java/org/apache/arrow/c/BufferImportTypeVisitor.java

@@ -187,7 +187,7 @@ public List<ArrowBuf> visit(ArrowType.Union type) {
 
   @Override
   public List<ArrowBuf> visit(ArrowType.RunEndEncoded type) {
-    throw new UnsupportedOperationException("Importing buffers for type: " + type);
+    return List.of();
   }
 
   @Override

java/c/src/main/java/org/apache/arrow/c/Format.java

@@ -233,6 +233,8 @@ static String asString(ArrowType arrowType) {
         return "+vl";
       case LargeListView:
         return "+vL";
+      case RunEndEncoded:
+        return "+r";
       case NONE:
         throw new IllegalArgumentException("Arrow type ID is NONE");
       default:
@@ -321,6 +323,8 @@ static ArrowType asType(String format, long flags)
         return new ArrowType.ListView();
       case "+vL":
         return new ArrowType.LargeListView();
+      case "+r":
+        return new ArrowType.RunEndEncoded();
       default:
         String[] parts = format.split(":", 2);
         if (parts.length == 2) {

java/c/src/test/java/org/apache/arrow/c/RoundtripTest.java

@@ -88,6 +88,7 @@
 import org.apache.arrow.vector.complex.ListVector;
 import org.apache.arrow.vector.complex.ListViewVector;
 import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.RunEndEncodedVector;
 import org.apache.arrow.vector.complex.StructVector;
 import org.apache.arrow.vector.complex.UnionVector;
 import org.apache.arrow.vector.complex.impl.UnionMapWriter;
@@ -770,6 +771,22 @@ public void testStructVector() {
     }
   }
 
+  @Test
+  public void testRunEndEncodedVector() {
+    try (final RunEndEncodedVector vector = RunEndEncodedVector.empty("v", allocator)) {
+      setVector(vector, List.of(1, 3), List.of(1, 2));
+      assertTrue(roundtrip(vector, RunEndEncodedVector.class));
+    }
+  }
+
+  @Test
+  public void testEmptyRunEndEncodedVector() {
+    try (final RunEndEncodedVector vector = RunEndEncodedVector.empty("v", allocator)) {
+      setVector(vector, List.of(), List.of());
+      assertTrue(roundtrip(vector, RunEndEncodedVector.class));
+    }
+  }
+
   @Test
   public void testExtensionTypeVector() {
     ExtensionTypeRegistry.register(new UuidType());

java/c/src/test/python/integration_tests.py

@@ -399,6 +399,20 @@ def recreate_batch():
                     return reader.read_next_batch()
 
         self.round_trip_record_batch(recreate_batch)
+
+    def test_runendencoded_array(self):
+        # empty vector
+        self.round_trip_array(lambda: pa.RunEndEncodedArray.from_arrays([], [], pa.run_end_encoded(pa.int64(), pa.int64())))
+
+        # constant null vector
+        self.round_trip_array(lambda: pa.RunEndEncodedArray.from_arrays([10], [None]))
+        # constant int vector
+        self.round_trip_array(lambda: pa.RunEndEncodedArray.from_arrays([10], [10]))
+
+        # run end int vector
+        self.round_trip_array(lambda: pa.RunEndEncodedArray.from_arrays([3, 5, 10, 12, 19], [1, 2, 1, None, 3]))
+        # run end string vector
+        self.round_trip_array(lambda: pa.RunEndEncodedArray.from_arrays([3, 5, 10, 12, 19], ["1", "2", "1", None, "3"]))
 
 if __name__ == '__main__':
     unittest.main(verbosity=2)

java/vector/src/main/java/org/apache/arrow/vector/complex/RunEndEncodedVector.java

@@ -30,8 +30,11 @@
 import org.apache.arrow.memory.util.hash.ArrowBufHasher;
 import org.apache.arrow.vector.BaseIntVector;
 import org.apache.arrow.vector.BaseValueVector;
+import org.apache.arrow.vector.BigIntVector;
 import org.apache.arrow.vector.BufferBacked;
 import org.apache.arrow.vector.FieldVector;
+import org.apache.arrow.vector.IntVector;
+import org.apache.arrow.vector.SmallIntVector;
 import org.apache.arrow.vector.ValueVector;
 import org.apache.arrow.vector.ZeroVector;
 import org.apache.arrow.vector.compare.VectorVisitor;
@@ -50,6 +53,7 @@
  * values vector of any type. There are no buffers associated with the parent vector.
  */
 public class RunEndEncodedVector extends BaseValueVector implements FieldVector {
+
   public static final FieldVector DEFAULT_VALUE_VECTOR = ZeroVector.INSTANCE;
   public static final FieldVector DEFAULT_RUN_END_VECTOR = ZeroVector.INSTANCE;
 
@@ -203,6 +207,7 @@ public void clear() {
     for (FieldVector v : getChildrenFromFields()) {
       v.clear();
     }
+    this.valueCount = 0;
   }
 
   /**
@@ -234,19 +239,6 @@ public MinorType getMinorType() {
     return MinorType.RUNENDENCODED;
   }
 
-  /**
-   * To transfer quota responsibility.
-   *
-   * @param allocator the target allocator
-   * @return a {@link org.apache.arrow.vector.util.TransferPair transfer pair}, creating a new
-   *     target vector of the same type.
-   */
-  @Override
-  public TransferPair getTransferPair(BufferAllocator allocator) {
-    throw new UnsupportedOperationException(
-        "RunEndEncodedVector does not support getTransferPair(BufferAllocator)");
-  }
-
   /**
    * To transfer quota responsibility.
    *
@@ -284,8 +276,7 @@ public TransferPair getTransferPair(Field field, BufferAllocator allocator) {
    */
   @Override
   public TransferPair getTransferPair(String ref, BufferAllocator allocator, CallBack callBack) {
-    throw new UnsupportedOperationException(
-        "RunEndEncodedVector does not support getTransferPair(String, BufferAllocator, CallBack)");
+    return new TransferImpl(ref, allocator, callBack);
   }
 
   /**
@@ -299,8 +290,7 @@ public TransferPair getTransferPair(String ref, BufferAllocator allocator, CallB
    */
   @Override
   public TransferPair getTransferPair(Field field, BufferAllocator allocator, CallBack callBack) {
-    throw new UnsupportedOperationException(
-        "RunEndEncodedVector does not support getTransferPair(Field, BufferAllocator, CallBack)");
+    return new TransferImpl(field, allocator, callBack);
   }
 
   /**
@@ -312,8 +302,156 @@ public TransferPair getTransferPair(Field field, BufferAllocator allocator, Call
    */
   @Override
   public TransferPair makeTransferPair(ValueVector target) {
-    throw new UnsupportedOperationException(
-        "RunEndEncodedVector does not support makeTransferPair(ValueVector)");
+    return new TransferImpl((RunEndEncodedVector) target);
+  }
+
+  private class TransferImpl implements TransferPair {
+
+    RunEndEncodedVector to;
+    TransferPair dataTransferPair;
+    TransferPair reeTransferPair;
+
+    public TransferImpl(String name, BufferAllocator allocator, CallBack callBack) {
+      this(new RunEndEncodedVector(name, allocator, field.getFieldType(), callBack));
+    }
+
+    public TransferImpl(Field field, BufferAllocator allocator, CallBack callBack) {
+      this(new RunEndEncodedVector(field, allocator, callBack));
+    }
+
+    public TransferImpl(RunEndEncodedVector to) {
+      this.to = to;
+      if (to.getRunEndsVector() instanceof ZeroVector) {
+        to.initializeChildrenFromFields(field.getChildren());
+      }
+      reeTransferPair = getRunEndsVector().makeTransferPair(to.getRunEndsVector());
+      dataTransferPair = getValuesVector().makeTransferPair(to.getValuesVector());
+    }
+
+    /**
+     * Transfer the vector data to another vector. The memory associated with this vector is
+     * transferred to the allocator of target vector for accounting and management purposes.
+     */
+    @Override
+    public void transfer() {
+      to.clear();
+      dataTransferPair.transfer();
+      reeTransferPair.transfer();
+      if (valueCount > 0) {
+        to.setValueCount(valueCount);
+      }
+      clear();
+    }
+
+    /**
+     * Slice this vector at the desired index and length, then transfer the corresponding data to
+     * the target vector.
+     *
+     * @param startIndex start position of the split in source vector.
+     * @param length length of the split.
+     */
+    @Override
+    public void splitAndTransfer(int startIndex, int length) {
+      to.clear();
+      if (length <= 0) {
+        return;
+      }
+
+      int physicalStartIndex = getPhysicalIndex(startIndex);
+      int physicalEndIndex = getPhysicalIndex(startIndex + length - 1);
+      int physicalLength = physicalEndIndex - physicalStartIndex + 1;
+      dataTransferPair.splitAndTransfer(physicalStartIndex, physicalLength);
+      FieldVector toRunEndsVector = to.runEndsVector;
+      if (startIndex == 0) {
+        if (((BaseIntVector) runEndsVector).getValueAsLong(physicalEndIndex) == length) {
+          reeTransferPair.splitAndTransfer(physicalStartIndex, physicalLength);
+        } else {
+          reeTransferPair.splitAndTransfer(physicalStartIndex, physicalLength - 1);
+          toRunEndsVector.setValueCount(physicalLength);
+          if (toRunEndsVector instanceof SmallIntVector) {
+            ((SmallIntVector) toRunEndsVector).set(physicalEndIndex, length);
+          } else if (toRunEndsVector instanceof IntVector) {
+            ((IntVector) toRunEndsVector).set(physicalEndIndex, length);
+          } else if (toRunEndsVector instanceof BigIntVector) {
+            ((BigIntVector) toRunEndsVector).set(physicalEndIndex, length);
+          } else {
+            throw new IllegalArgumentException(
+                "Run-end vector and must be of type int with size 16, 32, or 64 bits.");
+          }
+        }
+      } else {
+        shiftRunEndsVector(
+            toRunEndsVector,
+            startIndex,
+            length,
+            physicalStartIndex,
+            physicalEndIndex,
+            physicalLength);
+      }
+      getTo().setValueCount(length);
+    }
+
+    private void shiftRunEndsVector(
+        ValueVector toRunEndVector,
+        int startIndex,
+        int length,
+        int physicalStartIndex,
+        int physicalEndIndex,
+        int physicalLength) {
+      toRunEndVector.setValueCount(physicalLength);
+      toRunEndVector.getValidityBuffer().setOne(0, toRunEndVector.getValidityBuffer().capacity());
+      ArrowBuf fromRunEndBuffer = runEndsVector.getDataBuffer();
+      ArrowBuf toRunEndBuffer = toRunEndVector.getDataBuffer();
+      int physicalLastIndex = physicalLength - 1;
+      if (toRunEndVector instanceof SmallIntVector) {
+        byte typeWidth = SmallIntVector.TYPE_WIDTH;
+        for (int i = 0; i < physicalLastIndex; i++) {
+          toRunEndBuffer.setShort(
+              (long) i * typeWidth,
+              fromRunEndBuffer.getShort((long) (i + physicalStartIndex) * typeWidth) - startIndex);
+        }
+        int lastEnd =
+            Math.min(
+                fromRunEndBuffer.getShort((long) physicalEndIndex * typeWidth) - startIndex,
+                length);
+        toRunEndBuffer.setShort((long) physicalLastIndex * typeWidth, lastEnd);
+      } else if (toRunEndVector instanceof IntVector) {
+        byte typeWidth = IntVector.TYPE_WIDTH;
+        for (int i = 0; i < physicalLastIndex; i++) {
+          toRunEndBuffer.setInt(
+              (long) i * typeWidth,
+              fromRunEndBuffer.getInt((long) (i + physicalStartIndex) * typeWidth) - startIndex);
+        }
+        int lastEnd =
+            Math.min(
+                fromRunEndBuffer.getInt((long) physicalEndIndex * typeWidth) - startIndex, length);
+        toRunEndBuffer.setInt((long) physicalLastIndex * typeWidth, lastEnd);
+      } else if (toRunEndVector instanceof BigIntVector) {
+        byte typeWidth = BigIntVector.TYPE_WIDTH;
+        for (int i = 0; i < physicalLastIndex; i++) {
+          toRunEndBuffer.setLong(
+              (long) i * typeWidth,
+              fromRunEndBuffer.getLong((long) (i + physicalStartIndex) * typeWidth) - startIndex);
+        }
+        long lastEnd =
+            Math.min(
+                fromRunEndBuffer.getLong((long) physicalEndIndex * typeWidth) - startIndex, length);
+        toRunEndBuffer.setLong((long) physicalLastIndex * typeWidth, lastEnd);
+      } else {
+        throw new IllegalArgumentException(
+            "Run-end vector and must be of type int with size 16, 32, or 64 bits.");
+      }
+    }
+
+    @Override
+    public ValueVector getTo() {
+      return to;
+    }
+
+    @Override
+    public void copyValueSafe(int from, int to) {
+      this.to.copyFrom(from, to, RunEndEncodedVector.this);
+    }
   }
 
   /**
@@ -568,6 +706,7 @@ public void loadFieldBuffers(ArrowFieldNode fieldNode, List<ArrowBuf> ownBuffers
       throw new UnsupportedOperationException(
           "Run-end encoded vectors do not have any associated buffers.");
     }
+    this.valueCount = fieldNode.getLength();
   }
 
   /**

java/vector/src/main/java/org/apache/arrow/vector/ipc/JsonFileReader.java

@@ -909,10 +909,12 @@ private void readFromJsonIntoVector(Field field, FieldVector vector) throws IOEx
                 variadicBufferIndices));
       }
 
-      int nullCount = 0;
-      if (type instanceof ArrowType.Null) {
+      int nullCount;
+      if (type instanceof ArrowType.RunEndEncoded || type instanceof Union) {
+        nullCount = 0;
+      } else if (type instanceof ArrowType.Null) {
         nullCount = valueCount;
-      } else if (!(type instanceof Union)) {
+      } else {
         nullCount = BitVectorHelper.getNullCount(vectorBuffers.get(0), valueCount);
       }
       final ArrowFieldNode fieldNode = new ArrowFieldNode(valueCount, nullCount);

java/vector/src/main/java/org/apache/arrow/vector/validate/ValidateVectorBufferVisitor.java

@@ -305,7 +305,7 @@ public Void visit(RunEndEncodedVector vector, Void value) {
       if (runCount == 0) {
         validateOrThrow(valueCount == 0, "Run end vector does not contain enough elements");
       } else if (runCount > 0) {
-        double lastEnd = ((BaseIntVector) runEndsVector).getValueAsLong(runCount - 1);
+        long lastEnd = ((BaseIntVector) runEndsVector).getValueAsLong(runCount - 1);
         validateOrThrow(
             valueCount == lastEnd,
             "Vector logic length not equal to the last end in run ends vector. Logical length %s, last end %s",