Jingcheng Du commented on HBASE-17161:

Thanks Ram. For a mob cell, I think it is important.
In each scan of a mob-enabled cf, we try to read the ref tag. So it helps if 
the ref tag is in the first one.

> MOB : Make ref cell creation more efficient
> -------------------------------------------
>                 Key: HBASE-17161
>                 URL: https://issues.apache.org/jira/browse/HBASE-17161
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Anoop Sam John
>            Assignee: Anoop Sam John
>             Fix For: 2.0.0
>         Attachments: HBASE-17161.patch, HBASE-17161.patch
> When we flush MOB data, ref cells are created per actual MOB cell. This 
> creates lots of garbage
> Refer MobUtils#createMobRefCell
> We need to add 2 tags into the ref cell. An ArrayList is created with default 
> size creating ref array. Call to CellUtil.getTags will create a new ArrayList 
> even if the original cell is having no tags.
> A new KV is created which will create a new backing byte[] and do copy.  Also 
> along with each of the flush/compaction op, a fresh Tag object is created for 
> TableName tag.
> Fixes include
> 1. A table name tag is not going to change per HStore.  Even both the new 
> tags to be added.  Will keep a byte[] of these 2 tags at MobHStore level so 
> that all flush and compactions in this store can use it.
> 2. Create a new MobRefCell just like TagRewriteCell where only value and tags 
> part will be diff from the original cell.

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