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https://issues.apache.org/jira/browse/HBASE-15493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15206989#comment-15206989
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Vladimir Rodionov commented on HBASE-15493:
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Frankly speaking, I do not care about clueless users. Users I care about MUST
be able to read HBase source code and understand importance of hinting and
tweaking. This is just one of many small improvements which will follow soon.
If I will discard any small improvement just because it is not substantial
enough and I can't explain to regular user why is it for, I will never reach my
goal (purge all garbage in write and read path).
> Default ArrayList size may not be optimal for Mutation
> ------------------------------------------------------
>
> Key: HBASE-15493
> URL: https://issues.apache.org/jira/browse/HBASE-15493
> Project: HBase
> Issue Type: Improvement
> Components: Client, regionserver
> Affects Versions: 2.0.0
> Reporter: Vladimir Rodionov
> Assignee: Vladimir Rodionov
> Fix For: 2.0.0
>
> Attachments: HBASE-15493-v1.patch, HBASE-15493-v2.patch
>
>
> {code}
> List<Cell> getCellList(byte[] family) {
> List<Cell> list = this.familyMap.get(family);
> if (list == null) {
> list = new ArrayList<Cell>();
> }
> return list;
> }
> {code}
> Creates list of size 10, this is up to 80 bytes per column family in mutation
> object.
> Suggested:
> {code}
> List<Cell> getCellList(byte[] family) {
> List<Cell> list = this.familyMap.get(family);
> if (list == null) {
> list = new ArrayList<Cell>(CELL_LIST_INITIAL_CAPACITY);
> }
> return list;
> }
> {code}
> CELL_LIST_INITIAL_CAPACITY = 2 in the patch, this is debatable. For mutation
> where every CF has 1 cell, this gives decent reduction in memory allocation
> rate in both client and server during write workload. ~2%, not a big number,
> but as I said, already, memory optimization will include many small steps.
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