Yida Wu has submitted this change and it was merged. ( 
http://gerrit.cloudera.org:8080/24024 )

Change subject: IMPALA-14771: Fix DCHECK hit due to dangling reference in 
admission queue
......................................................................

IMPALA-14771: Fix DCHECK hit due to dangling reference in admission queue

This patch fixes two related issues. First, tests using
admission_control_rpc_compress_threshold_bytes were not applying the
flag correctly at cluster startup, so the compressed path was never
exercised. This is fixed by adding a helper in the tests to properly
inject the flag into impalad arguments.

Second, once compression was correctly enabled, during the tests, a
DCHECK was triggered in DequeueLoop when evaluating queued queries
with compressed execution requests. This happened because
SubmitForAdmission() calls ClearDecompressedCache() to free the
decompressed TQueryExecRequest while the query is queued, but
the group states (ScheduleState objects) still held references to
that freed request. When TryDequeue() later evaluated the query,
it accessed these dangling references and hit the DCHECK.

The fix clears group states immediately after clearing the
decompression cache and updates the schedule recompute logic so
group states are rebuilt when the query is dequeued.

Tests:
Passed test_admission_controller.py exhaustive tests.

Change-Id: I969e4f32b6838d305c317d0a75f17211f75eed57
Reviewed-on: http://gerrit.cloudera.org:8080/24024
Reviewed-by: Impala Public Jenkins <[email protected]>
Tested-by: Impala Public Jenkins <[email protected]>
---
M be/src/scheduling/admission-controller.cc
M be/src/scheduling/admission-controller.h
M tests/custom_cluster/test_admission_controller.py
3 files changed, 61 insertions(+), 12 deletions(-)

Approvals:
  Impala Public Jenkins: Looks good to me, approved; Verified

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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: I969e4f32b6838d305c317d0a75f17211f75eed57
Gerrit-Change-Number: 24024
Gerrit-PatchSet: 3
Gerrit-Owner: Yida Wu <[email protected]>
Gerrit-Reviewer: Abhishek Rawat <[email protected]>
Gerrit-Reviewer: Impala Public Jenkins <[email protected]>
Gerrit-Reviewer: Michael Smith <[email protected]>
Gerrit-Reviewer: Yida Wu <[email protected]>

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