[jira] [Assigned] (PHOENIX-6126) All createViewAddChildLink requests will go to the same region of SYSTEM.CHILD_LINK

["Viraj Jasani (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/PHOENIX-6126?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Viraj Jasani reassigned PHOENIX-6126:
-------------------------------------

    Assignee: Viraj Jasani

> All createViewAddChildLink requests will go to the same region of SYSTEM.CHILD_LINK
> -----------------------------------------------------------------------------------
>
>                 Key: PHOENIX-6126
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-6126
>             Project: Phoenix
>          Issue Type: Improvement
>    Affects Versions: 5.0.0, 4.15.0
>            Reporter: Chinmay Kulkarni
>            Assignee: Viraj Jasani
>            Priority: Minor
>             Fix For: 5.1.0, 4.16.0
>
>
> Currently, since there is no split policy defined for SYSTEM.CHILD_LINK, it can split by default.
> If SYSTEM.CHILD_LINK does split, then when the client invokes ConnectionQueryServices.childLinkMetaDataCoprocessorExec(), we always invoke the endpoint on the first region that contains linking rows for that parent (see [this|https://github.com/apache/phoenix/blob/e3c7b4bdce2524eb4fd1e7eb0ccd3454fcca81ce/phoenix-core/src/main/java/org/apache/phoenix/query/ConnectionQueryServicesImpl.java#L1629]). 
> Thus, no matter which region would actually contain the parent→child link, the first region is the one that has to always service the request and its RS finally issues the mutation to the correct region. Note that the mutateRowsWithLocks() call inside [ChildLinkMetaDataEndpoint.createViewAddChildLink()|https://github.com/apache/phoenix/blob/e3c7b4bdce2524eb4fd1e7eb0ccd3454fcca81ce/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/ChildLinkMetaDataEndpoint.java#L105] doesn’t fail even if the region doesn’t contain that row since we pass in an empty list for rowsToLock.
> During view creation, this request will lead to a Put of just 1 row and we have all the information to be able to pass in the exact row key instead of just the prefix (parent tenantId, parent schema, parent name). This should distribute load to all regions of SYSTEM.CHILD_LINK.



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