[Impala-ASF-CR] IMPALA-5776: Write partial tuple to the correct mempool

["Taras Bobrovytsky (Code Review)" <ge...@cloudera.org>]

Taras Bobrovytsky has uploaded a new patch set (#3).

Change subject: IMPALA-5776: Write partial tuple to the correct mempool
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IMPALA-5776: Write partial tuple to the correct mempool

In the text scanner, we were writing the partial tuple variable length
data to data_buffer_pool_ mempool which caused strange behavior, such
as incorrect results.

If we are scanning compressed data, the pool gets attached to the row
batch at the end of a GetNext() call and gets freed before the next
GetNext() call. This is wrong because we expect the data in the partial
tuple to survive between the GetNext() calls. If we are scanning non
compressed data, data_buffer_pool_ never gets cleared and grows over
time until the scanner finishes reading the scan range.

We fix the problem by creating a new memory pool for the partial tuple
will contains partial tuple contant length and variable length data.

Testing:
- Ran some tests locally on ASAN build.
- No new tests were added, because it is difficult to construct test
  cases due to the issue being non-deterministic.

Change-Id: I60ba5c113aefd17f697c1888fd46a237ef396540
---
M be/src/exec/hdfs-text-scanner.cc
M be/src/exec/hdfs-text-scanner.h
2 files changed, 29 insertions(+), 27 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/39/7639/3
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I60ba5c113aefd17f697c1888fd46a237ef396540
Gerrit-PatchSet: 3
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Taras Bobrovytsky <tb...@cloudera.com>
Gerrit-Reviewer: Alex Behm <al...@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <ta...@cloudera.com>