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Posted to issues@flink.apache.org by GitBox <gi...@apache.org> on 2022/01/20 11:01:35 UTC
[GitHub] [flink] Aitozi commented on a change in pull request #14893: [FLINK-21321][Runtime/StateBackends] improve RocksDB incremental rescale performance by using deleteRange operator
Aitozi commented on a change in pull request #14893:
URL: https://github.com/apache/flink/pull/14893#discussion_r788652085
##########
File path: flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBIncrementalCheckpointUtils.java
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@@ -122,30 +118,17 @@ private static void deleteRange(
RocksDB db,
List<ColumnFamilyHandle> columnFamilyHandles,
byte[] beginKeyBytes,
- byte[] endKeyBytes,
- @Nonnegative long writeBatchSize)
+ byte[] endKeyBytes)
throws RocksDBException {
for (ColumnFamilyHandle columnFamilyHandle : columnFamilyHandles) {
- try (ReadOptions readOptions = new ReadOptions();
- RocksIteratorWrapper iteratorWrapper =
- RocksDBOperationUtils.getRocksIterator(
- db, columnFamilyHandle, readOptions);
- RocksDBWriteBatchWrapper writeBatchWrapper =
- new RocksDBWriteBatchWrapper(db, writeBatchSize)) {
-
- iteratorWrapper.seek(beginKeyBytes);
-
- while (iteratorWrapper.isValid()) {
- final byte[] currentKey = iteratorWrapper.key();
- if (beforeThePrefixBytes(currentKey, endKeyBytes)) {
- writeBatchWrapper.remove(columnFamilyHandle, currentKey);
- } else {
- break;
- }
- iteratorWrapper.next();
- }
- }
+ // Using RocksDB's deleteRange will take advantage of delete
+ // tombstones, which mark the range as deleted. There are situations
+ // where tombstones can cause degraded performance, such as when
+ // too many tombstones are created.
+ //
+ // https://github.com/facebook/rocksdb/blob/bcd32560dd5898956b9d24553c2bb3c1b1d2319f/include/rocksdb/db.h#L357-L371
Review comment:
After looking into the [deleteRange implementations](https://rocksdb.org/blog/2018/11/21/delete-range.html) , I think the read path will not be affected too much, Because the deleted key range will not be query in current subtask.
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