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https://issues.apache.org/jira/browse/HBASE-8817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13702994#comment-13702994
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Thomas Pan commented on HBASE-8817:
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Here is the draft about scan. I just jot it down for my better understanding.
When client issues a scan against a table, Hbase generates RegionScanner
objects, one per region, to serve the scan request. RegionScanner object
contains a list of StoreScanner objects, one per column family. Each
StoreScanner object further contains a list of StoreFileScanner objects,
corresponding to each store file and HFile of the corresponding column family,
and a list of KeyValueScanner objects for memstore. The two lists are merge
into one, sorted in ascending order with scan object for memstore at the end of
the list. When a StoreFileScanner object is constructed, it is associated with
a MultiVersionConsistencyControl read point, which is the current memstoreTS at
the moment, filtering out any new updates beyond the read point.
> Enhance The Apache HBase Reference Guide
> ----------------------------------------
>
> Key: HBASE-8817
> URL: https://issues.apache.org/jira/browse/HBASE-8817
> Project: HBase
> Issue Type: Bug
> Components: documentation
> Reporter: Thomas Pan
>
> I am reading the guide here: http://hbase.apache.org/book.html#regions.arch
> I have noticed the following:
> - There is lack of coverage on scan. Note that Lars has a very good
> presentation from last year's HBaseCon:
> http://www.slideshare.net/cloudera/3-learning-h-base-internals-lars-hofhansl-salesforce-final
> - Under section 9.7.6.1, there is no mentioning of flush per region if a
> memstore reached the size threshold (and a possible flush of all memstores if
> over all memory usage of all the memstores reached memstore.upperlimit). Note
> that people need to combine the information provided in section 9 with
> section 2.3.1.1 to fully understand the situation.
> - Compaction tuning strategies. Both Nicolas from Facebook and Sergey from
> Hortonworks have presented various compaction algorithms. Sometime, once all
> the necessary code is in master, we need to have the coverage.
> Let me know how I can help on the matter.
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