[jira] [Commented] (HBASE-8073) HFileOutputFormat support for offline operation

["Jerry He (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-8073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13913397#comment-13913397 ] 

Jerry He commented on HBASE-8073:
---------------------------------

A good feature. 
An example is the WALPlayer. When replaying WALs to HFiles, it requires a live table with the same table name in the WAL, which makes it not useful as a offline tool.

> HFileOutputFormat support for offline operation
> -----------------------------------------------
>
>                 Key: HBASE-8073
>                 URL: https://issues.apache.org/jira/browse/HBASE-8073
>             Project: HBase
>          Issue Type: Sub-task
>          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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