[ https://issues.apache.org/jira/browse/FLINK-9070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16479058#comment-16479058 ]
ASF GitHub Bot commented on FLINK-9070: --------------------------------------- Github user sihuazhou commented on the issue: https://github.com/apache/flink/pull/5979 @StefanRRichter , the reason I prefer this approach is that: - From the comment in RocksDB's source we can find that deleteRange() should be used for deleting big range, what if the entries num of the map is not that big. - From the comments we can also find that deleteRange() would hurt the read performance, so we should consider to set ReadOptions::ignore_range_deletions = true to avoid the negative effect by deleteRange(), but if we use it for MapState.clear(), it seems that we can't set ReadOptions::ignore_range_deletions = true. And current approach should not bring any downside, what do you think? > Improve performance of RocksDBMapState.clear() > ---------------------------------------------- > > Key: FLINK-9070 > URL: https://issues.apache.org/jira/browse/FLINK-9070 > Project: Flink > Issue Type: Improvement > Components: State Backends, Checkpointing > Affects Versions: 1.6.0 > Reporter: Truong Duc Kien > Assignee: Sihua Zhou > Priority: Major > Fix For: 1.6.0 > > > Currently, RocksDBMapState.clear() is implemented by iterating over all the > keys and drop them one by one. This iteration can be quite slow with: > * Large maps > * High-churn maps with a lot of tombstones > There are a few methods to speed-up deletion for a range of keys, each with > their own caveats: > * DeleteRange: still experimental, likely buggy > * DeleteFilesInRange + CompactRange: only good for large ranges > > Flink can also keep a list of inserted keys in-memory, then directly delete > them without having to iterate over the Rocksdb database again. > > Reference: > * [RocksDB article about range > deletion|https://github.com/facebook/rocksdb/wiki/Delete-A-Range-Of-Keys] > * [Bug in DeleteRange|https://pingcap.com/blog/2017-09-08-rocksdbbug] > -- This message was sent by Atlassian JIRA (v7.6.3#76005)