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https://issues.apache.org/jira/browse/FLINK-9070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16469032#comment-16469032
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ASF GitHub Bot commented on FLINK-9070:
---------------------------------------
GitHub user sihuazhou opened a pull request:
https://github.com/apache/flink/pull/5979
[FLINK-9070][state]improve the performance of RocksDBMapState.clear()
## What is the purpose of the change
This PR intend to improve the performance of `RocksDBMapState.clear()` base
on the follow things:
- Using RocksIterator to iterate the records directly (currently we use the
RocksDBMapIterator, witch will buffer the records and may also need to perform
seeking multi times.)
- Using WriteBatch to perform deleting in bulk.
## Brief change log
- *improve the `RocksDBMapState.clear()` via iterating the records
directly and deleting records using WriteBatch.*
## Verifying this change
This change is already covered by existing tests,.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (no)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (no)
- The serializers: (no)
- The runtime per-record code paths (performance sensitive): (no)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
- The S3 file system connector: (no)
## Documentation
no
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/sihuazhou/flink improveMapStateClear
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/5979.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #5979
----
commit 969036a32b49b32a4168afb747dff54fe9ada6e6
Author: sihuazhou <summerleafs@...>
Date: 2018-04-07T13:52:05Z
improve the RocksDBMapState.clear() via iterate the records directly and
delete records using WriteBatch.
----
> 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]
>
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