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https://issues.apache.org/jira/browse/HBASE-4218?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13216331#comment-13216331
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Hudson commented on HBASE-4218:
-------------------------------
Integrated in HBase-TRUNK #2669 (See
[https://builds.apache.org/job/HBase-TRUNK/2669/])
[jira] [HBASE-5470] Make DataBlockEncodingTool work correctly with no native
compression codecs loaded
Summary:
DataBlockEncodingTool was fixed as part of porting data block encoding
(HBASE-4218) to 89-fb
(https://reviews.facebook.net/rHBASEEIGHTNINEFBBRANCH1245291,
https://reviews.facebook.net/D1659). The bug being fixed here appeared when
using GZ as baseline compression codec but not loading native Hadoop libraries,
in which case the compressor instance would be null.
Test Plan:
Run DataBlockEncoding tool with GZ (no native codecs) and LZO (with native
codecs) as baseline (Hadoop-level) compression codecs
Reviewers: JIRA, Kannan, mcorgan, lhofhansl, todd, stack, tedyu
Reviewed By: tedyu
Differential Revision: https://reviews.facebook.net/D1917 (Revision 1293057)
Result = SUCCESS
mbautin :
Files :
*
/hbase/trunk/src/test/java/org/apache/hadoop/hbase/regionserver/DataBlockEncodingTool.java
> Data Block Encoding of KeyValues (aka delta encoding / prefix compression)
> ---------------------------------------------------------------------------
>
> Key: HBASE-4218
> URL: https://issues.apache.org/jira/browse/HBASE-4218
> Project: HBase
> Issue Type: Improvement
> Components: io
> Affects Versions: 0.94.0
> Reporter: Jacek Migdal
> Assignee: Mikhail Bautin
> Labels: compression
> Fix For: 0.94.0
>
> Attachments: 0001-Delta-encoding-fixed-encoded-scanners.patch,
> 0001-Delta-encoding.patch, 4218-2012-01-14.txt, 4218-v16.txt, 4218.txt,
> D1659.1.patch, D1659.2.patch, D1659.3.patch, D447.1.patch, D447.10.patch,
> D447.11.patch, D447.12.patch, D447.13.patch, D447.14.patch, D447.15.patch,
> D447.16.patch, D447.17.patch, D447.18.patch, D447.19.patch, D447.2.patch,
> D447.20.patch, D447.21.patch, D447.22.patch, D447.23.patch, D447.24.patch,
> D447.25.patch, D447.26.patch, D447.3.patch, D447.4.patch, D447.5.patch,
> D447.6.patch, D447.7.patch, D447.8.patch, D447.9.patch,
> Data-block-encoding-2011-12-23.patch,
> Delta-encoding-2012-01-17_11_09_09.patch,
> Delta-encoding-2012-01-25_00_45_29.patch,
> Delta-encoding-2012-01-25_16_32_14.patch,
> Delta-encoding.patch-2011-12-22_11_52_07.patch,
> Delta-encoding.patch-2012-01-05_15_16_43.patch,
> Delta-encoding.patch-2012-01-05_16_31_44.patch,
> Delta-encoding.patch-2012-01-05_16_31_44_copy.patch,
> Delta-encoding.patch-2012-01-05_18_50_47.patch,
> Delta-encoding.patch-2012-01-07_14_12_48.patch,
> Delta-encoding.patch-2012-01-13_12_20_07.patch,
> Delta_encoding_with_memstore_TS.patch, open-source.diff
>
>
> A compression for keys. Keys are sorted in HFile and they are usually very
> similar. Because of that, it is possible to design better compression than
> general purpose algorithms,
> It is an additional step designed to be used in memory. It aims to save
> memory in cache as well as speeding seeks within HFileBlocks. It should
> improve performance a lot, if key lengths are larger than value lengths. For
> example, it makes a lot of sense to use it when value is a counter.
> Initial tests on real data (key length = ~ 90 bytes , value length = 8 bytes)
> shows that I could achieve decent level of compression:
> key compression ratio: 92%
> total compression ratio: 85%
> LZO on the same data: 85%
> LZO after delta encoding: 91%
> While having much better performance (20-80% faster decompression ratio than
> LZO). Moreover, it should allow far more efficient seeking which should
> improve performance a bit.
> It seems that a simple compression algorithms are good enough. Most of the
> savings are due to prefix compression, int128 encoding, timestamp diffs and
> bitfields to avoid duplication. That way, comparisons of compressed data can
> be much faster than a byte comparator (thanks to prefix compression and
> bitfields).
> In order to implement it in HBase two important changes in design will be
> needed:
> -solidify interface to HFileBlock / HFileReader Scanner to provide seeking
> and iterating; access to uncompressed buffer in HFileBlock will have bad
> performance
> -extend comparators to support comparison assuming that N first bytes are
> equal (or some fields are equal)
> Link to a discussion about something similar:
> http://search-hadoop.com/m/5aqGXJEnaD1/hbase+windows&subj=Re+prefix+compression
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