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https://issues.apache.org/jira/browse/KUDU-1600?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon resolved KUDU-1600.
-------------------------------
Resolution: Fixed
Assignee: Todd Lipcon
Fix Version/s: 1.3.0
Rather than disallow such encodings, I added some code in
d9bd5b8752efd4ae407043e491b7fd1e0b885a92 which automatically disables
compression on a per-block basis when the codec is found to not reach a target
compression ratio.
> Disallow enabling compression on already-compressed encodings
> -------------------------------------------------------------
>
> Key: KUDU-1600
> URL: https://issues.apache.org/jira/browse/KUDU-1600
> Project: Kudu
> Issue Type: Bug
> Components: cfile, master, perf
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Fix For: 1.3.0
>
>
> Some encodings (eg bitshuffle) are already compressed with LZ4, and enabling
> another pass of LZ4 compression on top of it just burns CPU. We should
> disallow such pairs of encodings.
> This is slightly trickier in the case of something like dictionary encoding,
> since it has the fallback path. For blocks that have fallen back to plain
> encoding, LZ4 is a good idea, whereas for blocks that are dict-encoded, the
> code words are already compressed and LZ4 is a waste.
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