aokolnychyi commented on code in PR #11463:
URL: https://github.com/apache/iceberg/pull/11463#discussion_r1828503271
##########
core/src/main/java/org/apache/iceberg/deletes/BitmapPositionDeleteIndex.java:
##########
@@ -92,4 +107,113 @@ public Collection<DeleteFile> deleteFiles() {
public long cardinality() {
return bitmap.cardinality();
}
+
+ /**
+ * Serializes the index using the following format:
+ *
+ * <ul>
+ * <li>The length of the magic bytes and bitmap stored as 4 bytes
(big-endian).
+ * <li>A 4-byte {@link #MAGIC_NUMBER} (little-endian).
+ * <li>The bitmap serialized using the portable Roaring spec
(little-endian).
+ * <li>A CRC-32 checksum of the magic bytes and bitmap as 4-bytes
(big-endian).
+ * </ul>
+ *
+ * Note that the length and the checksum are computed for the bitmap data,
which includes the
+ * magic bytes and bitmap for compatibility with Delta.
+ */
+ @Override
+ public ByteBuffer serialize() {
+ bitmap.runLengthEncode(); // run-length encode the bitmap before
serializing
+ int bitmapDataLength = computeBitmapDataLength(bitmap); // magic bytes +
bitmap
+ byte[] bytes = new byte[LENGTH_SIZE_BYTES + bitmapDataLength +
CRC_SIZE_BYTES];
+ ByteBuffer buffer = ByteBuffer.wrap(bytes);
+ buffer.putInt(bitmapDataLength);
+ serializeBitmapData(bytes, bitmapDataLength, bitmap);
+ int crcOffset = LENGTH_SIZE_BYTES + bitmapDataLength;
+ int crc = computeChecksum(bytes, bitmapDataLength);
+ buffer.putInt(crcOffset, crc);
+ buffer.rewind();
+ return buffer;
+ }
+
+ /**
+ * Deserializes the index from bytes, assuming the format described in
{@link #serialize()}.
+ *
+ * @param bytes an array containing the serialized index
+ * @param deleteFile the DV file
+ * @return the deserialized index
+ */
+ public static PositionDeleteIndex deserialize(byte[] bytes, DeleteFile
deleteFile) {
+ ByteBuffer buffer = ByteBuffer.wrap(bytes);
+ int bitmapDataLength = readBitmapDataLength(buffer, deleteFile);
+ RoaringPositionBitmap bitmap = deserializeBitmap(bytes, bitmapDataLength,
deleteFile);
+ int crc = computeChecksum(bytes, bitmapDataLength);
+ int crcOffset = LENGTH_SIZE_BYTES + bitmapDataLength;
+ int expectedCrc = buffer.getInt(crcOffset);
+ Preconditions.checkArgument(crc == expectedCrc, "Invalid CRC");
+ return new BitmapPositionDeleteIndex(bitmap, deleteFile);
+ }
+
+ // computes and validates the length of the bitmap data (magic bytes +
bitmap)
+ private static int computeBitmapDataLength(RoaringPositionBitmap bitmap) {
+ long length = MAGIC_NUMBER_SIZE_BYTES + bitmap.serializedSizeInBytes();
+ long bufferSize = LENGTH_SIZE_BYTES + length + CRC_SIZE_BYTES;
+ Preconditions.checkState(bufferSize <= Integer.MAX_VALUE, "Can't serialize
index > 2GB");
+ return (int) length;
+ }
+
+ // serializes the bitmap data (magic bytes + bitmap) using the little-endian
byte order
+ private static void serializeBitmapData(
+ byte[] bytes, int bitmapDataLength, RoaringPositionBitmap bitmap) {
+ ByteBuffer bitmapData = pointToBitmapData(bytes, bitmapDataLength);
+ bitmapData.putInt(MAGIC_NUMBER);
+ bitmap.serialize(bitmapData);
+ }
+
+ // points to the bitmap data in the blob
+ private static ByteBuffer pointToBitmapData(byte[] bytes, int
bitmapDataLength) {
+ ByteBuffer bitmapData = ByteBuffer.wrap(bytes, BITMAP_DATA_OFFSET,
bitmapDataLength);
+ bitmapData.order(ByteOrder.LITTLE_ENDIAN);
+ return bitmapData;
+ }
+
+ // checks the blob size is equal to the bitmap data length + extra bytes for
length and CRC
+ private static int readBitmapDataLength(ByteBuffer buffer, DeleteFile
deleteFile) {
+ int length = buffer.getInt();
+ long expectedLength = deleteFile.contentSizeInBytes() - LENGTH_SIZE_BYTES
- CRC_SIZE_BYTES;
+ Preconditions.checkArgument(
+ length == expectedLength,
+ "Invalid bitmap data length: %s, expected %s",
+ length,
+ expectedLength);
+ return length;
+ }
+
+ // validates magic bytes and deserializes the bitmap
+ private static RoaringPositionBitmap deserializeBitmap(
+ byte[] bytes, int bitmapDataLength, DeleteFile deleteFile) {
+ ByteBuffer bitmapData = pointToBitmapData(bytes, bitmapDataLength);
+ int magicNumber = bitmapData.getInt();
+ Preconditions.checkArgument(
+ magicNumber == MAGIC_NUMBER,
+ "Invalid magic number: %s, expected %s",
+ magicNumber,
+ MAGIC_NUMBER);
+ RoaringPositionBitmap bitmap =
RoaringPositionBitmap.deserialize(bitmapData);
+ long cardinality = bitmap.cardinality();
+ long expectedCardinality = deleteFile.recordCount();
Review Comment:
Did this for consistency with the method above. It shouldn't be expensive to
call `recordCount()` twice, so I am OK changing it.
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