[jira] [Updated] (PHOENIX-6154) Move the check for existence of child views and task addition to drop those child views to the client side when dropping a table/view

["Chinmay Kulkarni (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/PHOENIX-6154?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Chinmay Kulkarni updated PHOENIX-6154:
--------------------------------------
    Fix Version/s:     (was: 4.16.0)
                   4.16.1

> Move the check for existence of child views and task addition to drop those child views to the client side when dropping a table/view
> -------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: PHOENIX-6154
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-6154
>             Project: Phoenix
>          Issue Type: Sub-task
>    Affects Versions: 5.0.0, 4.15.0
>            Reporter: Chinmay Kulkarni
>            Priority: Major
>             Fix For: 5.1.0, 4.16.1
>
>
> When we issue a {{DROP TABLE/VIEW}}, if the table/view being dropped has child views (and {{CASCADE}} is provided), we add a {{[DropChildViewsTask|https://github.com/apache/phoenix/blob/1d844950bb4ec8221873ecd2b094c20f427cd984/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/tasks/DropChildViewsTask.java]}} in the {{SYSTEM.TASK}} table (see [this|https://github.com/apache/phoenix/blob/1d844950bb4ec8221873ecd2b094c20f427cd984/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/MetaDataEndpointImpl.java#L2479]). This means that *while holding the row lock* for the table/view’s header row ([here|https://github.com/apache/phoenix/blob/1d844950bb4ec8221873ecd2b094c20f427cd984/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/MetaDataEndpointImpl.java#L2253]) we do the following:
>  # Make an [RPC|https://github.com/apache/phoenix/blob/1d844950bb4ec8221873ecd2b094c20f427cd984/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/MetaDataEndpointImpl.java#L2459-L2461] to the region hosting {{SYSTEM.CHILD_LINK}} to scan it in order to find child views.
>  # If any child views are found in the step above, we make additional RPCs to the region hosting {{SYSTEM.TASK}} to {{[UPSERT|https://github.com/apache/phoenix/blob/1d844950bb4ec8221873ecd2b094c20f427cd984/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/MetaDataEndpointImpl.java#L2479-L2484]}} a {{DropChildViewsTask}} for immediate child views.
>  # We [send remote mutations|https://github.com/apache/phoenix/blob/1d844950bb4ec8221873ecd2b094c20f427cd984/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/MetaDataEndpointImpl.java#L2298-L2302] to drop parent→child links from the {{SYSTEM.CHILD_LINK}} table.
> Of the above extra RPCs, note that even if the table/view has no child views or if {{CASCADE}} is not provided, we will still do the first RPC from the server while holding a row lock.
> We should move this check to the client (issue a scan against SYSTEM.CHILD_LINK to see if a single linking row exists) and also add the task from the client.



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