pgaref opened a new pull request #2215:
URL: https://github.com/apache/hive/pull/2215
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### What changes were proposed in this pull request?
Victim Task (A) should be preempted in favor of a candidate Task (B) when:
1. A is NOT on the same DAG and Vertex as B AND
1.1. B is a Guaranteed Task while A is not OR
1.2. Both are guaranteed but A is not finishable and B is
To make sure that Victim task is not behind some upstream updates
(asynchronous), we check its sources' state (by QueryFragmentInfo.canFinish
method)
### Why are the changes needed?
Non-useful Task preemptions can increase query latency
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Updated TestTaskExecutorService.testFinishablePreemptsNonFinishable()
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