[HIVE-10242] ACID: insert overwrite prevents create table command

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.0.0
• Fix Version/s: 1.2.0
• Component/s: Transactions
• Assignee: Eugene Koifman
• Reporter: Eugene Koifman
• Created: 07/Apr/15 19:02
• Updated: 01/Oct/19 22:07
• Resolved: 16/Apr/15 18:00

Description

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)

Issue Links

• breaks: HIVE-15077 Acid LockManager is unfair
• is related to: HIVE-12594 X lock on partition should not conflict with S lock on DB