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https://issues.apache.org/jira/browse/HBASE-14221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14699486#comment-14699486
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Hadoop QA commented on HBASE-14221:
-----------------------------------
{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12750790/HBASE-14221_1.patch
against master branch at commit 737f264509284420e6fa8c14d92fe9fbdb49f67f.
ATTACHMENT ID: 12750790
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:red}-1 tests included{color}. The patch doesn't appear to include
any new or modified tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
{color:red}-1 javac{color}. The patch appears to cause mvn compile goal to
fail with Hadoop version 2.4.0.
Compilation errors resume:
[ERROR] COMPILATION ERROR :
[ERROR]
/home/jenkins/jenkins-slave/workspace/PreCommit-HBASE-Build/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ReversedRegionScannerImpl.java:[67,3]
method does not override or implement a method from a supertype
[ERROR] Failed to execute goal
org.apache.maven.plugins:maven-compiler-plugin:3.2:compile (default-compile) on
project hbase-server: Compilation failure
[ERROR]
/home/jenkins/jenkins-slave/workspace/PreCommit-HBASE-Build/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ReversedRegionScannerImpl.java:[67,3]
method does not override or implement a method from a supertype
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e
switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please
read the following articles:
[ERROR] [Help 1]
http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
[ERROR]
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR] mvn <goals> -rf :hbase-server
Console output:
https://builds.apache.org/job/PreCommit-HBASE-Build/15129//console
This message is automatically generated.
> Reduce the number of time row comparison is done in a Scan
> ----------------------------------------------------------
>
> Key: HBASE-14221
> URL: https://issues.apache.org/jira/browse/HBASE-14221
> Project: HBase
> Issue Type: Sub-task
> Components: Scanners
> Reporter: ramkrishna.s.vasudevan
> Assignee: ramkrishna.s.vasudevan
> Fix For: 2.0.0
>
> Attachments: HBASE-14221.patch, HBASE-14221_1.patch,
> withmatchingRowspatch.png, withoutmatchingRowspatch.png
>
>
> When we tried to do some profiling with the PE tool found this.
> Currently we do row comparisons in 3 places in a simple Scan case.
> 1) ScanQueryMatcher
> {code}
> int ret = this.rowComparator.compareRows(curCell, cell);
> if (!this.isReversed) {
> if (ret <= -1) {
> return MatchCode.DONE;
> } else if (ret >= 1) {
> // could optimize this, if necessary?
> // Could also be called SEEK_TO_CURRENT_ROW, but this
> // should be rare/never happens.
> return MatchCode.SEEK_NEXT_ROW;
> }
> } else {
> if (ret <= -1) {
> return MatchCode.SEEK_NEXT_ROW;
> } else if (ret >= 1) {
> return MatchCode.DONE;
> }
> }
> {code}
> 2) In StoreScanner next() while starting to scan the row
> {code}
> if (!scannerContext.hasAnyLimit(LimitScope.BETWEEN_CELLS) ||
> matcher.curCell == null ||
> isNewRow || !CellUtil.matchingRow(peeked, matcher.curCell)) {
> this.countPerRow = 0;
> matcher.setToNewRow(peeked);
> }
> {code}
> Particularly to see if we are in a new row.
> 3) In HRegion
> {code}
> scannerContext.setKeepProgress(true);
> heap.next(results, scannerContext);
> scannerContext.setKeepProgress(tmpKeepProgress);
> nextKv = heap.peek();
> moreCellsInRow = moreCellsInRow(nextKv, currentRowCell);
> {code}
> Here again there are cases where we need to careful for a MultiCF case. Was
> trying to solve this for the MultiCF case but is having lot of cases to
> solve. But atleast for a single CF case I think these comparison can be
> reduced.
> So for a single CF case in the SQM we are able to find if we have crossed a
> row using the code pasted above in SQM. That comparison is definitely needed.
> Now in case of a single CF the HRegion is going to have only one element in
> the heap and so the 3rd comparison can surely be avoided if the
> StoreScanner.next() was over due to MatchCode.DONE caused by SQM.
> Coming to the 2nd compareRows that we do in StoreScanner. next() - even that
> can be avoided if we know that the previous next() call was over due to a new
> row. Doing all this I found that the compareRows in the profiler which was
> 19% got reduced to 13%. Initially we can solve for single CF case which can
> be extended to MultiCF cases.
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