[GitHub] GJL commented on a change in pull request #6510: [State TTL] Swap serialization order in TTL value: first timestamp then user value

[GitBox <gi...@apache.org>]

GJL commented on a change in pull request #6510: [State TTL] Swap serialization order in TTL value: first timestamp then user value
URL: https://github.com/apache/flink/pull/6510#discussion_r208210641
 
 

 ##########
 File path: flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBMapState.java
 ##########
 @@ -625,4 +630,74 @@ private void loadCache() {
 			(Map<UK, UV>) stateDesc.getDefaultValue(),
 			backend);
 	}
+
+	/**
+	 * RocksDB map state specific byte value transformer wrapper.
+	 *
+	 * <p>This specific transformer wrapper checks the first byte to detect null user value entries
+	 * and if not null forward the rest of byte array to the original byte value transformer.
+	 */
+	static class StateSnapshotTransformerWrapper implements StateSnapshotTransformer<byte[]> {
+		private static final byte[] NULL_VALUE;
+		private static final byte NON_NULL_VALUE_PREFIX;
+		static {
+			ByteArrayDataOutputView dov = new ByteArrayDataOutputView(1);
+			try {
+				dov.writeBoolean(true);
+				NULL_VALUE = dov.toByteArray();
+				dov.reset();
+				dov.writeBoolean(false);
+				NON_NULL_VALUE_PREFIX = dov.toByteArray()[0];
+			} catch (IOException e) {
+				throw new FlinkRuntimeException("Failed to serialize boolean flag of map user null value", e);
+			}
+		}
+
+		private final StateSnapshotTransformer<byte[]> elementTransformer;
+		private final ByteArrayDataInputView div;
+
+		StateSnapshotTransformerWrapper(StateSnapshotTransformer<byte[]> originalTransformer) {
+			this.elementTransformer = originalTransformer;
+			this.div = new ByteArrayDataInputView();
+		}
+
+		@Override
+		@Nullable
+		public byte[] filterOrTransform(@Nullable byte[] value) {
+			if (value == null || isNull(value)) {
+				return NULL_VALUE;
+			} else {
+				// we have to skip the first byte indicating null user value
+				// TODO: optimization here cauld be to work with slices and not byte arrays
 
 Review comment:
   nit: *could*

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