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https://issues.apache.org/jira/browse/HBASE-4608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13175314#comment-13175314
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jirapos...@reviews.apache.org commented on HBASE-4608:
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bq. On 2011-12-23 06:34:53, Lars Hofhansl wrote:
bq. >
src/main/java/org/apache/hadoop/hbase/regionserver/wal/SimpleDictionary.java,
line 73
bq. > <https://reviews.apache.org/r/2740/diff/2/?file=65772#file65772line73>
bq. >
bq. > What if you have a hash collision?
bq. > You now overwrite the old value that just happens to have the same
hash code. Is that OK?
I overwrite the old value. As long as we do it for both reads and writes, thats
okay! (The state of the dictionary must be consistent).
bq. On 2011-12-23 06:34:53, Lars Hofhansl wrote:
bq. >
src/main/java/org/apache/hadoop/hbase/regionserver/wal/SimpleDictionary.java,
line 82
bq. > <https://reviews.apache.org/r/2740/diff/2/?file=65772#file65772line82>
bq. >
bq. > Here too; what happens for hash collisions?
The old value would have been evicted by the latest value.
bq. On 2011-12-23 06:34:53, Lars Hofhansl wrote:
bq. >
src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestWALReplay.java, line
84
bq. > <https://reviews.apache.org/r/2740/diff/2/?file=65775#file65775line84>
bq. >
bq. > I assume you'll tests with/without compression.
I'm gonna write better tests, this is just sort of a hackwish way to make it
work.
bq. On 2011-12-23 06:34:53, Lars Hofhansl wrote:
bq. > src/main/java/org/apache/hadoop/hbase/regionserver/wal/WALEdit.java,
line 130
bq. > <https://reviews.apache.org/r/2740/diff/2/?file=65774#file65774line130>
bq. >
bq. > Would sure be nice if we had a KeyValue interface and the
implementations would just do the right thing.
Didn't want to create a new KeyValue, or modify it, rather - thus the
CompressedKeyValue thing.
I can refactor this.
- Li
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On 2011-12-23 06:00:24, Li Pi wrote:
bq.
bq. -----------------------------------------------------------
bq. This is an automatically generated e-mail. To reply, visit:
bq. https://reviews.apache.org/r/2740/
bq. -----------------------------------------------------------
bq.
bq. (Updated 2011-12-23 06:00:24)
bq.
bq.
bq. Review request for hbase, Eli Collins and Todd Lipcon.
bq.
bq.
bq. Summary
bq. -------
bq.
bq. Heres what I have so far. Things are written, and "should work". I need to
rework the test cases to test this, and put something in the config file to
enable/disable. Obviously this isn't ready for commit at the moment, but I can
get those two things done pretty quickly.
bq.
bq. Obviously the dictionary is incredibly simple at the moment, I'll come up
with something cooler sooner. Let me know how this looks.
bq.
bq.
bq. This addresses bug HBase-4608.
bq. https://issues.apache.org/jira/browse/HBase-4608
bq.
bq.
bq. Diffs
bq. -----
bq.
bq.
src/main/java/org/apache/hadoop/hbase/regionserver/wal/CompressedKeyValue.java
PRE-CREATION
bq. src/main/java/org/apache/hadoop/hbase/regionserver/wal/Compressor.java
PRE-CREATION
bq. src/main/java/org/apache/hadoop/hbase/regionserver/wal/HLog.java 24407af
bq. src/main/java/org/apache/hadoop/hbase/regionserver/wal/HLogKey.java
f067221
bq.
src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceFileLogReader.java
d9cd6de
bq.
src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceFileLogWriter.java
cbef70f
bq.
src/main/java/org/apache/hadoop/hbase/regionserver/wal/SimpleDictionary.java
PRE-CREATION
bq.
src/main/java/org/apache/hadoop/hbase/regionserver/wal/WALDictionary.java
PRE-CREATION
bq. src/main/java/org/apache/hadoop/hbase/regionserver/wal/WALEdit.java
e1117ef
bq.
src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestWALReplay.java
59910bf
bq.
bq. Diff: https://reviews.apache.org/r/2740/diff
bq.
bq.
bq. Testing
bq. -------
bq.
bq.
bq. Thanks,
bq.
bq. Li
bq.
bq.
> HLog Compression
> ----------------
>
> Key: HBASE-4608
> URL: https://issues.apache.org/jira/browse/HBASE-4608
> Project: HBase
> Issue Type: New Feature
> Reporter: Li Pi
> Assignee: Li Pi
> Attachments: 4608v1.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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