[HIVE-24291] Compaction Cleaner prematurely cleans up deltas

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-alpha-1
• Labels: pull-request-available
• Assignee: Peter Varga
• Reporter: Peter Varga
• Created: 20/Oct/20 11:49
• Updated: 06/Apr/24 10:45
• Resolved: 03/Nov/20 08:42

Description

Since HIVE-23107 the cleaner can clean up deltas that are still used by running queries.

Example:

• TxnId 1-5 writes to a partition, all commits
• Compactor starts with txnId=6
• Long running query starts with txnId=7, it sees txnId=6 as open in its snapshot
• Compaction commits
• Cleaner runs

Previously min_history_level table would have prevented the Cleaner to delete the deltas1-5 until txnId=7 is open, but now they will be deleted and the long running query may fail if its tries to access the files.

Solution could be to not run the cleaner until any txn is open that was opened before the compaction was committed (CQ_NEXT_TXN_ID)

Issue Links

• contains: HIVE-24314 compactor.Cleaner should not set state "mark cleaned" if it didn't remove any files
• fixes: HIVE-23107 Remove MIN_HISTORY_LEVEL table
• links to: GitHub Pull Request #1592