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https://issues.apache.org/jira/browse/PHOENIX-3534?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16533107#comment-16533107
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ASF GitHub Bot commented on PHOENIX-3534:
-----------------------------------------

Github user JamesRTaylor commented on the issue:

    https://github.com/apache/phoenix/pull/303
  
    +1 to the patch. Great work @twdsilva and @churrodog! I made some minor 
comments for some potential follow up work and had a few questions, but let's 
get this committed first. I'd recommend the following priority for the next 
JIRA as:
    
    1. Move views to their own table
    2. Get rid of client side code that is sending the base columns
    3. Fix corner case/race condition issues
    4. Add code that doesn't write orphaned metadata on major compaction


> Support multi region SYSTEM.CATALOG table
> -----------------------------------------
>
>                 Key: PHOENIX-3534
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-3534
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: James Taylor
>            Assignee: Thomas D'Silva
>            Priority: Major
>             Fix For: 5.0.0, 4.15.0
>
>         Attachments: PHOENIX-3534.patch
>
>
> Currently Phoenix requires that the SYSTEM.CATALOG table is single region 
> based on the server-side row locks being held for operations that impact a 
> table and all of it's views. For example, adding/removing a column from a 
> base table pushes this change to all views.
> As an alternative to making the SYSTEM.CATALOG transactional (PHOENIX-2431), 
> when a new table is created we can do a lazy cleanup  of any rows that may be 
> left over from a failed DDL call (kudos to [~lhofhansl] for coming up with 
> this idea). To implement this efficiently, we'd need to also do PHOENIX-2051 
> so that we can efficiently find derived views.
> The implementation would rely on an optimistic concurrency model based on 
> checking our sequence numbers for each table/view before/after updating. Each 
> table/view row would be individually locked for their change (metadata for a 
> view or table cannot span regions due to our split policy), with the sequence 
> number being incremented under lock and then returned to the client.



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