[jira] [Commented] (HIVE-26555) Read-only mode for Hive database

["László Bodor (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-26555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17620299#comment-17620299 ] 

László Bodor commented on HIVE-26555:
-------------------------------------

design question: can you please describe what kind of failover/fail-back scenarios are you referring to and how exactly a read-only database is a solution in that event? thanks!

> Read-only mode for Hive database
> --------------------------------
>
>                 Key: HIVE-26555
>                 URL: https://issues.apache.org/jira/browse/HIVE-26555
>             Project: Hive
>          Issue Type: New Feature
>            Reporter: Teddy Choi
>            Assignee: Teddy Choi
>            Priority: Minor
>              Labels: pull-request-available
>             Fix For: 4.0.0-alpha-2
>
>          Time Spent: 1h
>  Remaining Estimate: 0h
>
> h1. Purpose
> In failover/fail-back scenarios, a Hive database needs to be read-only, while other one is writable to keep a single source of truth.
> h1. User-Facing Changes
> Yes. EnforceReadOnlyDatabaseHook class implements ExecuteWithHookContext interface. hive.exec.pre.hooks needs to have the class name to initiate an instance. The "readonly" database property can be configured to turn it on and off.
> h2. Allowed read operations
> All read operations without any data/metadata change are allowed.
>  * EXPLAIN
>  * USE(or SWITCHDATABASE)
>  * REPLDUMP
>  * REPLSTATUS
>  * EXPORT
>  * KILL_QUERY
>  * DESC prefix
>  * SHOW prefix
>  * QUERY with SELECT or EXPLAIN. INSERT, DELETE, UPDATE are disallowed.
> h2. Allowed write operations
> Most of write operations that change data/metadata are disallowed. There are few allowed exceptions. The first one is alter database to make a database writable. The second one is replication load to load a dumped database.
>  * ALTER DATABASE db_name SET DBPROPERTIES without "readonly"="true".
>  * REPLLOAD
> h1. Tests
>  * read_only_hook.q: USE, SHOW, DESC, DESCRIBE, EXPLAIN, SELECT
>  * read_only_delete.q
>  * read_only_insert.q



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