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https://issues.apache.org/jira/browse/ACCUMULO-112?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13725598#comment-13725598
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ASF subversion and git services commented on ACCUMULO-112:
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Commit 0608e32f8b09f926e40677d1e23ccedd0d6e088d in branch refs/heads/master
from [~keith_turner]
[ https://git-wip-us.apache.org/repos/asf?p=accumulo.git;h=0608e32 ]
ACCUMULO-112 added locality group support to in memory map
> Investigate partitioning in memory map by locality group
> --------------------------------------------------------
>
> Key: ACCUMULO-112
> URL: https://issues.apache.org/jira/browse/ACCUMULO-112
> Project: Accumulo
> Issue Type: Task
> Components: tserver
> Reporter: Keith Turner
> Assignee: Keith Turner
> Labels: gsoc2013, mentor
>
> Currently the in memory map is not partitioned by locality group. This could
> negatively impact scan and minor compaction performance. Would like to run
> some experiments to understand the performance implications. Partitioning by
> locality group could negatively impact insert performance, it could go from
> O(log(R)+log(C)) to O(L * (log(R)+log(C))) in the worst case. L is the
> number of locality groups, R is the number of rows and C is the number of
> columns. The worst case is where each mutation has a change for each
> locality group.
> Currently the in memory map is a map of maps. Like the following.
> {noformat}
> map<row, map<col, val>>
> {noformat}
> Could conceptually change this to one of the following. The first is best
> for scans, that access some locality groups, and minor compactions. The
> second is good for inserts where the mutation covers all locality groups,
> because the row is only looked up once.
> {noformat}
> map<localityGroup, map<row, map<col, val>>>
> {noformat}
> {noformat}
> map<row, map<localityGroup, map<col, val>>>
> {noformat}
> The Accumulo native map is implemented using C++,STL, JNI, and with thread
> locking in java.
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