Aditya Shah created HIVE-23724:
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Summary: Hive ACID Lock conflicts not getting resolved correctly.
Key: HIVE-23724
URL: https://issues.apache.org/jira/browse/HIVE-23724
Project: Hive
Issue Type: Bug
Components: Transactions
Affects Versions: 3.1.2
Reporter: Aditya Shah
Assignee: Aditya Shah
Steps to reproduce:
1. `Drop database temp cascade`
2. Parallelly (after 1. but while 1. is running) fire a `create table
temp.temp_table (a int, b int) clustered by (a) into 2 buckets stored as orc
TBLPROPERTIES ('transactional'='true')`
3. Parallelly (after 2. but while 2. is running) fire a `insert overwrite table
temp.temp_table values (1,2)`
note: The above could be easily reproduced by a unit test in testDbTxnManager.
Observation: Exclusive lock for Table in 3. is granted although exclusive lock
for DB acquired in 1. is still acquired and shared read lock on DB for 2. is
waiting.
Cause of issue: while acquiring a lock if we choose to ignore a conflict
between the desired lock and one of the existing locks we immediately allow the
desired lock to be acquired without checking against all the existing locks.
The above-mentioned scenario was one such ignore conflict condition in 2. and
3. There could be other possible combinations where this may occur. Like for
example when we request a lock with the same txn ids. Although hive guarantees
that this scenario will not occur due to all lock requests related to a txn are
asked at the same and failure of one guarantees failure of all, we in future
will have to be extra careful with it.
Resolution: Whenever we ignore conflict we should keep looking against all the
existing locks and only then allow the lock to be acquired.
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