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https://issues.apache.org/jira/browse/HIVE-10242?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14498411#comment-14498411
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Eugene Koifman commented on HIVE-10242:
---------------------------------------
The fix also logging improvements and a fix to the following situation where a
lock (by client3) could be acquired when it should not be.
client1: update table T
client2: select * from T
client3: update table T
with all 3 clients executing concurrently and starting in above order, client 3
should be blocked until client1 finishes.
> ACID: insert overwrite prevents create table command
> ----------------------------------------------------
>
> Key: HIVE-10242
> URL: https://issues.apache.org/jira/browse/HIVE-10242
> Project: Hive
> Issue Type: Bug
> Components: Transactions
> Affects Versions: 1.0.0
> Reporter: Eugene Koifman
> Assignee: Eugene Koifman
> Fix For: 1.2.0
>
> Attachments: HIVE-10242.2.patch, HIVE-10242.3.patch,
> HIVE-10242.4.patch, HIVE-10242.patch
>
>
> 1. insert overwirte table DB.T1 select ... from T2: this takes X lock on
> DB.T1 and S lock on T2.
> X lock makes sense because we don't want anyone reading T1 while it's
> overwritten. S lock on T2 prevents if from being dropped while the query is
> in progress.
> 2. create table DB.T3: takes S lock on DB.
> This S lock gets blocked by X lock on T1. S lock prevents the DB from being
> dropped while create table is executed.
> If the insert statement is long running, this blocks DDL ops on the same
> database. This is a usability issue.
> There is no good reason why X lock on a table within a DB and S lock on DB
> should be in conflict.
> (this is different from a situation where X lock is on a partition and S lock
> is on the table to which this partition belongs. Here it makes sense.
> Basically there is no SQL way to address all tables in a DB but you can
> easily refer to all partitions of a table)
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