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https://issues.apache.org/jira/browse/HBASE-4218?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13123337#comment-13123337
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Jacek Migdal commented on HBASE-4218:
-------------------------------------
Performance results on production data.
CopyKeyDeltaEncoder:
Compression performance: 1136.33 MB/s (+/- 60.91 MB/s)
Decompression performance: 373.29 MB/s (+/- 281.22 MB/s)
BitsetKeyDeltaEncoder:
Compression performance: 147.57 MB/s (+/- 0.58 MB/s)
Decompression performance: 166.78 MB/s (+/- 54.81 MB/s)
PrefixKeyDeltaEncoder:
Compression performance: 293.94 MB/s (+/- 1.97 MB/s)
Decompression performance: 233.61 MB/s (+/- 91.97 MB/s)
FastDiffDeltaEncoder:
Compression performance: 203.47 MB/s (+/- 0.37 MB/s)
Decompression performance: 196.77 MB/s (+/- 43.22 MB/s)
DiffKeyDeltaEncoder:
Compression performance: 187.74 MB/s (+/- 0.24 MB/s)
Decompression performance: 163.13 MB/s (+/- 12.17 MB/s)
LZO:
Compression performance: 260.35 MB/s (+/- 0.76 MB/s)
Decompression performance: 173.45 MB/s (+/- 76.13 MB/s)
CopyKeyDeltaEncoder
Saved bytes: -4
Key compression ratio: -0.00 %
All compression ratio: -0.00 %
LZO compressed size: 152019
LZO compression ratio: 85.79 %
BitsetKeyDeltaEncoder
Saved bytes: 747061
Key compression ratio: 75.46 %
All compression ratio: 69.82 %
LZO compressed size: 124438
LZO compression ratio: 88.37 %
PrefixKeyDeltaEncoder
Saved bytes: 831602
Key compression ratio: 84.00 %
All compression ratio: 77.72 %
LZO compressed size: 117285
LZO compression ratio: 89.04 %
FastDiffDeltaEncoder
Saved bytes: 935275
Key compression ratio: 94.47 %
All compression ratio: 87.41 %
LZO compressed size: 94360
LZO compression ratio: 91.18 %
DiffKeyDeltaEncoder
Saved bytes: 909175
Key compression ratio: 91.84 %
All compression ratio: 84.97 %
LZO compressed size: 96597
LZO compression ratio: 90.97 %
Total KV prefix length: 80000
Total key length: 910000
Total key redundancy: 781606
Total value length: 80000
DeltaEncodingSeekPerformance
BlockDeltaEncoder onDisk='NONE' inCache='NONE' inMemory=false
Read speed: 63.99 (MB/s)
Seeks per second: 54901.21 (#/s)
BlockDeltaEncoder onDisk='NONE' inCache='BITSET' inMemory=false
Read speed: 46.73 (MB/s)
Seeks per second: 13570.50 (#/s)
BlockDeltaEncoder onDisk='NONE' inCache='PREFIX' inMemory=false
Read speed: 55.88 (MB/s)
Seeks per second: 20298.89 (#/s)
BlockDeltaEncoder onDisk='NONE' inCache='DIFF' inMemory=false
Read speed: 54.39 (MB/s)
Seeks per second: 15082.79 (#/s)
BlockDeltaEncoder onDisk='NONE' inCache='FAST_DIFF' inMemory=false
Read speed: 54.12 (MB/s)
Seeks per second: 15432.61 (#/s)
BlockDeltaEncoder onDisk='NONE' inCache='NONE' inMemory=true
Read speed: 64.37 (MB/s)
Seeks per second: 56779.82 (#/s)
BlockDeltaEncoder onDisk='NONE' inCache='BITSET' inMemory=true
Read speed: 35.42 (MB/s)
Seeks per second: 46170.87 (#/s)
BlockDeltaEncoder onDisk='NONE' inCache='PREFIX' inMemory=true
Read speed: 43.54 (MB/s)
Seeks per second: 60108.48 (#/s)
BlockDeltaEncoder onDisk='NONE' inCache='DIFF' inMemory=true
Read speed: 40.62 (MB/s)
Seeks per second: 48779.68 (#/s)
BlockDeltaEncoder onDisk='NONE' inCache='FAST_DIFF' inMemory=true
Read speed: 40.76 (MB/s)
Seeks per second: 57291.22 (#/s)
> Delta Encoding of KeyValues (aka 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
> Labels: compression
> Attachments: 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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