[FLINK-8639] Fix always need to seek multiple times when iterator RocksDBMapState

• Type: Improvement
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.4.0
• Fix Version/s: 1.5.0
• Component/s: Runtime / State Backends
• Assignee: Sihua Zhou
• Reporter: Sihua Zhou
• Created: 12/Feb/18 14:39
• Updated: 15/Jul/19 08:51
• Resolved: 22/Feb/18 15:04

Description

Currently, almost every time we want to iterator a RocksDBMapState we need to do seek at least 2 times (Seek is a poor performance action for rocksdb cause it can't use the bloomfilter). This is because `RocksDBMapIterator` use a `cacheEntries` to cache the seek values every time and the `cacheEntries`'s init size is 1.

Issue Links

• causes: FLINK-13034 Improve the performance when checking whether mapstate is empty for RocksDBStateBackend
• links to: GitHub Pull Request #5465