[jira] [Created] (HIVE-10242) ACID: insert overwrite prevents create table command

["Eugene Koifman (JIRA)" <ji...@apache.org>]

Eugene Koifman created HIVE-10242:
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             Summary: 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


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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