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https://issues.apache.org/jira/browse/HBASE-4608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13228965#comment-13228965
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stack commented on HBASE-4608:
------------------------------
bq. It implies that WAL_VERSION is the same as COMPRESSION_VERSION.
Yes. Thats right. The current global version is the version that introduces
WAL compression.
bq. As I explained earlier, we would likely have another compression scheme for
WAL in the future, resulting in the introduction of PREFIX_COMPRESSION_VERSION
You are conflating wal version and compression type. They are not the same
thing.
If we introduce a new compression type only, and if all else is equal -- same
API, etc. -- then we don't need to up the global version. We are just adding a
new compression type. Either we support it or we don't. If we don't we'll
throw unsupported compression type (the dictionary compression type is
currently called DICTIONARY_COMPRESSION_TYPE).
> HLog Compression
> ----------------
>
> Key: HBASE-4608
> URL: https://issues.apache.org/jira/browse/HBASE-4608
> Project: HBase
> Issue Type: New Feature
> Reporter: Li Pi
> Assignee: stack
> Fix For: 0.94.0
>
> Attachments: 4608-v19.txt, 4608-v20.txt, 4608-v22.txt, 4608v1.txt,
> 4608v13.txt, 4608v13.txt, 4608v14.txt, 4608v15.txt, 4608v16.txt, 4608v17.txt,
> 4608v18.txt, 4608v23.txt, 4608v24.txt, 4608v25.txt, 4608v5.txt, 4608v6.txt,
> 4608v7.txt, 4608v8fixed.txt
>
>
> The current bottleneck to HBase write speed is replicating the WAL appends
> across different datanodes. We can speed up this process by compressing the
> HLog. Current plan involves using a dictionary to compress table name, region
> id, cf name, and possibly other bits of repeated data. Also, HLog format may
> be changed in other ways to produce a smaller HLog.
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