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From "Tim Armstrong (Code Review)" <>
Subject [Impala-ASF-CR] IMPALA-5713: always reserve memory for preaggs
Date Wed, 23 Aug 2017 23:18:17 GMT
Hello Dan Hecht,

I'd like you to reexamine a change.  Please visit

to look at the new patch set (#4).

Change subject: IMPALA-5713: always reserve memory for preaggs

IMPALA-5713: always reserve memory for preaggs

Before this change the preaggregation was frequently disabled when
running under some memory pressure, e.g. if the aggregation is at the
end of a pipeline of joins and those joins eat up all the memory.
This can result in huge performance degradation since all rows must then
be sent over the network.

This change always reserves 16 * (buffer size + 64kb) bytes per
preaggregation so that it is always able to build some hash tables and
reduce the input somewhat.

This has two parts:
* Changing the frontend reservation calculation
* Removing dead code in the backend that handled the case when the
  initial partitions and hash tables could not be allocated.

Passes exhaustive tests.

Change-Id: I2b544f9ec1a906719e2bbb074743926b95a3a573
M be/src/exec/
M be/src/exec/
M be/src/exec/partitioned-aggregation-node.h
M fe/src/main/java/org/apache/impala/planner/
M testdata/workloads/functional-planner/queries/PlannerTest/max-row-size.test
M testdata/workloads/functional-planner/queries/PlannerTest/mt-dop-validation.test
M testdata/workloads/functional-planner/queries/PlannerTest/resource-requirements.test
M testdata/workloads/functional-planner/queries/PlannerTest/spillable-buffer-sizing.test
M testdata/workloads/functional-query/queries/QueryTest/spilling-aggs.test
9 files changed, 109 insertions(+), 119 deletions(-)

  git pull ssh:// refs/changes/39/7739/4
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I2b544f9ec1a906719e2bbb074743926b95a3a573
Gerrit-PatchSet: 4
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tim Armstrong <>
Gerrit-Reviewer: Dan Hecht <>
Gerrit-Reviewer: Tim Armstrong <>

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