Eugene Koifman created HIVE-15077: ------------------------------------- Summary: Acid LockManager is unfair Key: HIVE-15077 URL: https://issues.apache.org/jira/browse/HIVE-15077 Project: Hive Issue Type: Bug Components: Transactions Reporter: Eugene Koifman Assignee: Eugene Koifman
HIVE-10242 made the acid LM unfair. In TxnHandler.checkLock(), suppose we are trying to acquire SR5 (the number is extLockId). Then LockInfo[] locks = lockSet.toArray(new LockInfo[lockSet.size()]); may look like this (all explicitly listed locks are in Waiting state) {...., SR5 SW3 X4} So the algorithm will find SR5 in the list and start looking backwards. According to IDs, SR5 should wait for X4 to be granted but X4 won't even be examined and so SR5 may be granted. Theoretically, this could cause starvation. The query that generates the list already has query.append(" and hl_lock_ext_id <= ").append(extLockId); but it should use "<" rather than "<=" to exclude the locks being checked from "locks" list which will make the algorithm look at all locks "in front" of a given lock. -- This message was sent by Atlassian JIRA (v6.3.4#6332)