[Impala-ASF-CR] IMPALA-6588: don't add empty list of ranges in text scan

["Tim Armstrong (Code Review)" <ge...@cloudera.org>]

Tim Armstrong has uploaded a new patch set (#2). ( http://gerrit.cloudera.org:8080/9456 )

Change subject: IMPALA-6588: don't add empty list of ranges in text scan
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IMPALA-6588: don't add empty list of ranges in text scan

DiskIoMgr::AddScanRanges() can returned CANCELLED even when adding an
empty list of scan ranges. We should avoid adding empty lists of
scan ranges, specifically after a scan has completed.

This patch fixes HdfsTextScanner::IssueInitialRanges() to avoid the
anti-pattern of adding empty lists of scan ranges.

Testing:
Ran core tests.

Looped the table sample and scanner tests for a while.

Change-Id: I661a9e234fb87ebdd2596519b44ffba0d7e91d4c
---
M be/src/exec/hdfs-scan-node-base.cc
M be/src/exec/hdfs-text-scanner.cc
M be/src/runtime/io/disk-io-mgr.cc
3 files changed, 6 insertions(+), 2 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/56/9456/2
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I661a9e234fb87ebdd2596519b44ffba0d7e91d4c
Gerrit-Change-Number: 9456
Gerrit-PatchSet: 2
Gerrit-Owner: Tim Armstrong <ta...@cloudera.com>