Jingcheng Du commented on HBASE-16578:

Thanks a lot for review [~te...@apache.org]! I will upload a patch to address 
bq. The original test is superseded by the new test ?
Yes, the new test support the old one.

> Mob data loss after mob compaction and normal compcation
> --------------------------------------------------------
>                 Key: HBASE-16578
>                 URL: https://issues.apache.org/jira/browse/HBASE-16578
>             Project: HBase
>          Issue Type: Bug
>          Components: mob
>    Affects Versions: 2.0.0
>            Reporter: huaxiang sun
>            Assignee: Jingcheng Du
>         Attachments: HBASE-16578.patch, TestMobCompaction.java, 
> TestMobCompaction.java
> StoreFileScanners on MOB cells rely on the scannerOrder to find the latest 
> cells after mob compaction. The value of scannerOrder is assigned by the 
> order of maxSeqId of StoreFile, and this maxSeqId is valued only after the 
> reader of the StoreFile is created.
> In {{Compactor.compact}}, the compacted store files are cloned and their 
> readers are not created. And in {{StoreFileScanner.getScannersForStoreFiles}} 
> the StoreFiles are sorted before the readers are created and at that time the 
> maxSeqId for each file is -1 (the default value). This will lead  to a chaos 
> in scanners in the following normal compaction. Some older cells might be 
> chosen during the normal compaction.
> We need to create readers either before the sorting in the method 
> {{StoreFileScanner.getScannersForStoreFiles}}, or create readers just after 
> the store files are cloned in {{Compactor.compact}}.

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