Myasuka commented on code in PR #20405:
URL: https://github.com/apache/flink/pull/20405#discussion_r940311495
##########
flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/AbstractRocksDBState.java:
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@@ -223,4 +223,27 @@ public StateIncrementalVisitor<K, N, V>
getStateIncrementalVisitor(
throw new UnsupportedOperationException(
"Global state entry iterator is unsupported for RocksDb
backend");
}
+
+ /**
+ * Similar to decimal addition, add 1 to the last digit to calculate the
upper bound.
+ *
+ * @param prefix the starting prefix for seek.
+ * @return end prefix for seek.
+ */
+ protected final byte[] calculateUpperBound(byte[] prefix) {
+ byte[] upperBound = new byte[prefix.length];
+ System.arraycopy(prefix, 0, upperBound, 0, prefix.length);
+ boolean overFlow = true;
+ for (int i = prefix.length - 1; i >= 0; i--) {
+ int unsignedValue = prefix[i] & 0xff;
+ int result = unsignedValue + 1;
+ upperBound[i] = (byte) (result & 0xff);
+ if (result >> 8 == 0) {
+ overFlow = false;
+ break;
+ }
+ }
+ Preconditions.checkArgument(!overFlow, "The upper boundary
overflows.");
Review Comment:
It's my bad to give the wrong description of the binary format of `127`.
You can run the code below:
~~~java
int maxKeyGroup = 127;
int keyGroupPrefixBytes =
CompositeKeySerializationUtils.computeRequiredBytesInKeyGroupPrefix(
maxKeyGroup + 1);
byte[] bytes = new byte[keyGroupPrefixBytes];
bytes[0] = extractByteAtPosition(maxKeyGroup, 0);;
byte[] upperBound = calculateUpperBound(bytes);
~~~
And you will get the byte array of `upperBound` as `[-128]`, from my mind,
changing `0x7f` to `0x80` for a single byte is a kind of **overflow**. However,
this is legal in your code, which would make other developers confused.
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