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https://issues.apache.org/jira/browse/HBASE-9583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13776731#comment-13776731
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Jean-Marc Spaggiari commented on HBASE-9583:
--------------------------------------------
Some might want to take a look took because I'm neither native English, but
here is my review:
{code}
Before HBASE-7845, while finalizing a data block (e.g. reach blocksize setting
or close file), HBase picks up the start key of current data block as an index
entry adding into the current leaf index block, however in some way, indexing
on the stop key of previous data block can be treated as a better choice (see
HBASE-5987 and HBASE-4443 for more details). It's not an easy thing to change
this behavior without refactoring lots of low level codes. HBASE-7845
implemented the getShortMidpointKey method which is similar with Leveldb's
ByteWiseComparatorImpl::FindShortestSeparator() and FindShortSuccessor(). The
core of getShortMidpointKey is to generate a "virtual" key bigger than the stop
key of previous data block, and smaller or equal to the start key of the
current data block. The gap between the stop key of previous data block and the
"virtual" key is as small as possible. Also we make sure that the length of the
"virtual" key is as small as possible. e.g. the stop key of previous block is
"the quick brown fox", the start key of current block is "the who", then
getShortMidpointKey can generate a "virtual" key like "the r" as the new index
entry. It brings two benefits at least:1) Reduce the hfile data index size. 2)
Avoid extra seeking to the previous data block request if the target key is in
the range of ["virtual key","start key of current block"]
{code}
> add document for getShortMidpointKey
> ------------------------------------
>
> Key: HBASE-9583
> URL: https://issues.apache.org/jira/browse/HBASE-9583
> Project: HBase
> Issue Type: Task
> Components: HFile
> Affects Versions: 0.98.0
> Reporter: Liang Xie
> Assignee: Liang Xie
> Attachments: HBase-9583.txt
>
>
> add the faked key to documentation http://hbase.apache.org/book.html#hfilev2
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