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https://issues.apache.org/jira/browse/HBASE-8073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13599550#comment-13599550
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Ted Yu commented on HBASE-8073:
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+1.
Nice feature.
> HFileOutputFormat support for offline operation
> -----------------------------------------------
>
> Key: HBASE-8073
> URL: https://issues.apache.org/jira/browse/HBASE-8073
> Project: HBase
> Issue Type: New Feature
> Components: mapreduce
> Reporter: Nick Dimiduk
>
> When using HFileOutputFormat to generate HFiles, it inspects the region
> topology of the target table. The split points from that table are used to
> guide the TotalOrderPartitioner. If the target table does not exist, it is
> first created. This imposes an unnecessary dependence on an online HBase and
> existing table.
> If the table exists, it can be used. However, the job can be smarter. For
> example, if there's far more data going into the HFiles than the table
> currently contains, the table regions aren't very useful for data split
> points. Instead, the input data can be sampled to produce split points more
> meaningful to the dataset. LoadIncrementalHFiles is already capable of
> handling divergence between HFile boundaries and table regions, so this
> should not pose any additional burdon at load time.
> The proper method of sampling the data likely requires a custom input format
> and an additional map-reduce job perform the sampling. See a relevant
> implementation:
> https://github.com/alexholmes/hadoop-book/blob/master/src/main/java/com/manning/hip/ch4/sampler/ReservoirSamplerInputFormat.java
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