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https://issues.apache.org/jira/browse/HBASE-3484?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13025463#comment-13025463
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Joe Pallas commented on HBASE-3484:
-----------------------------------
This issue was cited by jdcryans as related to unfortunate performance seen in
the following case:
A test program fills a single row of a family with tens of thousands of
sequentially increasing qualifiers. Then it performs random gets (or exists)
of those qualifiers. The response time seen is (on average) proportional to
the ordinal position of the qualifier. If the table is flushed before the
random tests begin, then the average response time is basically constant,
independent of the qualifier's ordinal position.
I'm not sure that either of the two points in the description actually covers
this case, but I don't know enough to say.
> 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
> Affects Versions: 0.92.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Fix For: 0.92.0
>
>
> 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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