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
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}
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