[jira] [Commented] (HBASE-4389) Address lots of issues with migration from 90 to trunk

["stack (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-4389?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13133306#comment-13133306 ] 

stack commented on HBASE-4389:
------------------------------

Patch in hbase-4388 addresses some of above.

+ It increments HRI VERSION (and makes HRI able to deserialize the old format that has HTD)
+ We no longer have a migrated flag but a version in root for meta table (a short)
+ Migration should be idempotent now; we look at each row and check its HRI VERSION and if not current, do update
+ Duplicated code has been removed
+ We no longer do createTableDescriptor on each HRI scanned; just on the first.

Outstanding:

+ Migration code has been coalesced some but still code spread about
+ There is no sanity checking that all HTDs for a table are equal. Not sure what we'd do if they were not equal other than warn.  We wouldn't know which of them all to take.  Patch in hbase-4388 takes the first regions HTD.  This is usually the first updated; later updates could fail so its the first is likely the 'latest' iteration on HTD I'd guess.
                
> Address lots of issues with migration from 90 to trunk
> ------------------------------------------------------
>
>                 Key: HBASE-4389
>                 URL: https://issues.apache.org/jira/browse/HBASE-4389
>             Project: HBase
>          Issue Type: Bug
>          Components: master, migration
>    Affects Versions: 0.92.0
>            Reporter: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.92.0
>
>
> Looking over the migration code that removes HTD from HRI, there are lots of issues. This JIRA is to redo this code in a way that will be less bug prone, and also future proof.

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