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From: "stack (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-15493) Default ArrayList size may not be
 optimal for Mutation
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    [ https://issues.apache.org/jira/browse/HBASE-15493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15206874#comment-15206874 ] 

stack commented on HBASE-15493:
-------------------------------

Agreed user will not know what to do w/ this new API  "Save an unknown and unmeasurable amount of resources serverside by setting this value... " This is not the sort of stuff we should be bothering our users with. Before you know, a mythology will build up that playing with this setting is the difference between cluster life and death. Lets just do the work serverside for the user and not bother them with such minuitae.

> 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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