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https://issues.apache.org/jira/browse/HIVE-15796?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15858543#comment-15858543
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Hive QA commented on HIVE-15796:
--------------------------------
Here are the results of testing the latest attachment:
https://issues.apache.org/jira/secure/attachment/12851711/HIVE-15796.2.patch
{color:red}ERROR:{color} -1 due to no test(s) being added or modified.
{color:red}ERROR:{color} -1 due to 4 failed/errored test(s), 10242 tests
executed
*Failed tests:*
{noformat}
TestDerbyConnector - did not produce a TEST-*.xml file (likely timed out)
(batchId=235)
org.apache.hadoop.hive.cli.TestEncryptedHDFSCliDriver.testCliDriver[encryption_join_with_different_encryption_keys]
(batchId=159)
org.apache.hadoop.hive.cli.TestPerfCliDriver.testCliDriver[query14]
(batchId=223)
org.apache.hadoop.hive.cli.TestPerfCliDriver.testCliDriver[query23]
(batchId=223)
{noformat}
Test results: https://builds.apache.org/job/PreCommit-HIVE-Build/3445/testReport
Console output: https://builds.apache.org/job/PreCommit-HIVE-Build/3445/console
Test logs: http://104.198.109.242/logs/PreCommit-HIVE-Build-3445/
Messages:
{noformat}
Executing org.apache.hive.ptest.execution.TestCheckPhase
Executing org.apache.hive.ptest.execution.PrepPhase
Executing org.apache.hive.ptest.execution.ExecutionPhase
Executing org.apache.hive.ptest.execution.ReportingPhase
Tests exited with: TestsFailedException: 4 tests failed
{noformat}
This message is automatically generated.
ATTACHMENT ID: 12851711 - PreCommit-HIVE-Build
> HoS: poor reducer parallelism when operator stats are not accurate
> ------------------------------------------------------------------
>
> Key: HIVE-15796
> URL: https://issues.apache.org/jira/browse/HIVE-15796
> Project: Hive
> Issue Type: Improvement
> Components: Statistics
> Affects Versions: 2.2.0
> Reporter: Chao Sun
> Assignee: Chao Sun
> Attachments: HIVE-15796.1.patch, HIVE-15796.2.patch,
> HIVE-15796.wip.1.patch, HIVE-15796.wip.2.patch, HIVE-15796.wip.patch
>
>
> In HoS we use currently use operator stats to determine reducer parallelism.
> However, it is often the case that operator stats are not accurate,
> especially if column stats are not available. This sometimes will generate
> extremely poor reducer parallelism, and cause HoS query to run forever.
> This JIRA tries to offer an alternative way to compute reducer parallelism,
> similar to how MR does. Here's the approach we are suggesting:
> 1. when computing the parallelism for a MapWork, use stats associated with
> the TableScan operator;
> 2. when computing the parallelism for a ReduceWork, use the *maximum*
> parallelism from all its parents.
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