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https://issues.apache.org/jira/browse/HBASE-3484?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13850170#comment-13850170
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Lars Hofhansl commented on HBASE-3484:
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>From [~mcorgan]...
bq. I've been pondering how to better compact the data in the memstore.
Sometimes we see a 100MB memstore flush that is really 10MB of KeyValues, which
gzips to like 2MB, meaning there is a ton of pointer overhead.
This should better now. In various patches I removed:
* caching of the row key (HBASE-7279)
* caching of the timestamp (HBASE-7279)
* caching of the KV length (HBASE-9956)
That saves 12 bytes + sizeOf(rowKey) for each KeyValue in the memstore.
The KV in memory overhead now is: 56 bytes. (the memstoreTS is also stored in
the HFiles).
> Replace memstore's ConcurrentSkipListMap with our own implementation
> --------------------------------------------------------------------
>
> Key: HBASE-3484
> URL: https://issues.apache.org/jira/browse/HBASE-3484
> Project: HBase
> Issue Type: Improvement
> Components: Performance
> Affects Versions: 0.92.0
> Reporter: Todd Lipcon
> Priority: Critical
> Attachments: WIP_HBASE-3484.patch, hierarchical-map.txt,
> memstore_drag.png
>
>
> By copy-pasting ConcurrentSkipListMap into HBase we can make two improvements
> to it for our use case in MemStore:
> - add an iterator.replace() method which should allow us to do upsert much
> more cheaply
> - implement a Set directly without having to do Map<KeyValue,KeyValue> to
> save one reference per entry
> It turns out CSLM is in public domain from its development as part of JSR
> 166, so we should be OK with licenses.
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