apurtell opened a new pull request #3802:
URL: https://github.com/apache/hbase/pull/3802


   This integration test emulates a use case that stores a lot of small values 
into a table that would likely be heavily indexed (ROW_INDEX_V1, small blocks, 
etc.), an application that crowdsources weather (temperature) observation data. 
This IT can be used to test and optimize compression settings for such cases. 
It comes with a companion utility, HFileBlockExtracter, which extracts block 
data from HFiles into a set of local files for use in training external 
compression dictionaries, perhaps with ZStandard's `zstd` utility.
   
   Run like:
   
       ./bin/hbase org.apache.hadoop.hbase.test.IntegrationTestLoadSmallValues
          numRows numMappers outputDir
   
   You can also split the Loader and Verify stages:
   
   Load with:
   
       ./bin/hbase 
'org.apache.hadoop.hbase.test.IntegrationTestLoadSmallValues$Loader'
          numRows numMappers outputDir
   
   Verify with:
   
       ./bin/hbase 
'org.apache.hadoop.hbase.test.IntegrationTestLoadSmallValues$Verify'
          outputDir
   
   Use HFileExtractor like so:
   
       ./bin/hbase org.apache.hadoop.hbase.test.util.HFileExtractor
          options outputDir hfile_1 ... hfile_n
   
   Where options are:
   
        -d : Width of generated file name for zero padding, default: 5 
        -n : Total number of blocks to extract, default: unlimited 
        -r | --random: Shuffle blocks and write them in randomized order
   
   You might train ZStandard dictionaries on the extracted block files like so:
   (Assumes outputDir given to HFileExtractor was 't'.)
   
       $ zstd --train -o dict t/*
   
   Or:
   
       $ zstd --train-fastcover=k=32,d=6 -o dict t/*


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