Re: Review Request: Reseeking directly to required columns

[Pranav Khaitan <pr...@gmail.com>]

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trunk/src/main/java/org/apache/hadoop/hbase/regionserver/ScanQueryMatcher.java
<http://review.cloudera.org/r/781/#comment4769>

    Kannan, what you are suggesting is the right thing to do but I don't think it is required much here. This function is called only when the ScanQueryMatcher decides that it wants to go to the next column (and not next row). If the ScanQueryMatcher knows that all columns are over, then it will return SEEK_NEXT_ROW instead of SEEK_NEXT_COL. In that case, this function will never be called. Therefore, nextColumn will only be null when we are using WildcardColumnTracker and do not have explicit column information.


- Pranav


On 2010-09-16 00:57:12, Pranav Khaitan wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> http://review.cloudera.org/r/781/
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> 
> (Updated 2010-09-16 00:57:12)
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> Review request for hbase, stack, Jonathan Gray, Karthik Ranganathan, and Kannan Muthukkaruppan.
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> 
> Summary
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> Optimize reads for specific columns by reseeking between scans. Use the reseek logic to jump directly to next required column rather than reading current column.
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> Big performance gain for queries with sparse columns. Not advantageous for dense ones. Consider this before comitting.
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> Further suggestions/questions are welcome!
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> This addresses bugs HBASE-2450, HBASE-2916 and HBASE-2959.
>     http://issues.apache.org/jira/browse/HBASE-2450
>     http://issues.apache.org/jira/browse/HBASE-2916
>     http://issues.apache.org/jira/browse/HBASE-2959
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> 
> Diffs
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>   trunk/src/main/java/org/apache/hadoop/hbase/HConstants.java 990674 
>   trunk/src/main/java/org/apache/hadoop/hbase/KeyValue.java 990674 
>   trunk/src/main/java/org/apache/hadoop/hbase/regionserver/ScanQueryMatcher.java 990674 
>   trunk/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java 990674 
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> Diff: http://review.cloudera.org/r/781/diff
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> Testing
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> All existing tests pass and make significant use of this code. 
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> Added a new test file called TestColumnSeeking along with another patch at https://review.cloudera.org/r/780/.
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> Thanks,
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> Pranav
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>