[HIVE-23349] ACID: Concurrent MERGE INSERT operations produce duplicates

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-alpha-1
• Component/s: Transactions
• Assignee: Denys Kuzmenko
• Reporter: Denys Kuzmenko
• Created: 30/Apr/20 19:25
• Updated: 17/Nov/22 08:50
• Resolved: 11/May/20 07:43

Description

2 concurrent MERGE INSERT operations generate duplicates due to lack of locking.
MERGE INSERT is treated as regular INSERT, it acquires SHARED_READ lock that doesn't prevent other INSERTs. We should use EXCLUSIVE lock here or EXCL_WRITE if hive.txn.write.xlock=false;

create table target (a int, b int) stored as orc TBLPROPERTIES ('transactional'='true')");
insert into target values (1,2), (3,4)
create table source (a int, b int)

execute in parallel:

insert into source values (5,6), (7,8)

Issue Links

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