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https://issues.apache.org/jira/browse/HBASE-10752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13941985#comment-13941985
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Ted Yu commented on HBASE-10752:
--------------------------------
Patch v3 applies to 0.98
Here is what I tested with 0.98 + patch v3:
1. loaded up new hbase-server.jar
2. scanned an existing table - on rs-status#blockCacheStats UI, observed 0
cache eviction
3. performed schema change to use FAST_DIFF encoding:
{code}
hbase(main):001:0> alter 'testtable', {DATA_BLOCK_ENCODING => 'FAST_DIFF'}
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in
[jar:file:/usr/lib/hadoop/lib/slf4j-log4j12-1.7.5.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in
[jar:file:/usr/lib/zookeeper/lib/slf4j-log4j12-1.6.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
2014-03-20 17:10:49,893 WARN [main] conf.Configuration: hbase-site.xml:an
attempt to override final parameter: dfs.support.append; Ignoring.
2014-03-20 17:10:50,424 WARN [main] conf.Configuration: hbase-site.xml:an
attempt to override final parameter: dfs.support.append; Ignoring.
2014-03-20 17:10:50,481 WARN [main] conf.Configuration: hbase-site.xml:an
attempt to override final parameter: dfs.support.append; Ignoring.
Unknown argument ignored: DATA_BLOCK_ENCODING
Updating all regions with the new schema...
0/1 regions updated.
1/1 regions updated.
Done.
0 row(s) in 4.2120 seconds
{code}
4. scanned the table one more time - observed cache eviction increase
> Port HBASE-10270 'Remove DataBlockEncoding from BlockCacheKey' to trunk
> -----------------------------------------------------------------------
>
> Key: HBASE-10752
> URL: https://issues.apache.org/jira/browse/HBASE-10752
> Project: HBase
> Issue Type: Improvement
> Reporter: Ted Yu
> Assignee: Ted Yu
> Priority: Minor
> Fix For: 0.99.0
>
> Attachments: 10752-v1.txt, 10752-v2.txt, 10752-v3.txt, 10752-v4.txt
>
>
> The JIRA removes the block encoding from the key and forces the caller of
> HFileReaderV2.readBlock() to specify the expected BlockType as well as the
> expected DataBlockEncoding when these matter. This allows for a decision on
> either of these at read time instead of cache time, puts responsibility where
> appropriate, fixes some cache misses when using the scan preloading (which
> does a read without knowing the type or encoding), allows for the
> BlockCacheKey to be re-used by the L2 BucketCache and sets us up for a future
> CompoundScannerV2 which can read both un-encoded and encoded data blocks.
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