[jira] [Commented] (PHOENIX-3534) Support multi region SYSTEM.CATALOG table

["churro morales (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PHOENIX-3534?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15935402#comment-15935402 ] 

churro morales commented on PHOENIX-3534:
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Hey folks I thought I would add a doc to document this approach and what considerations we should be making. 

> 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: Samarth Jain
>
> 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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