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From "Hive QA (JIRA)" <>
Subject [jira] [Commented] (HIVE-11638) ExprNodeDesc hashMap accidentally degrades into O(N) instead of O(1)
Date Tue, 25 Aug 2015 19:52:45 GMT


Hive QA commented on HIVE-11638:

{color:red}Overall{color}: -1 at least one tests failed

Here are the results of testing the latest attachment:

{color:red}ERROR:{color} -1 due to 1 failed/errored test(s), 9377 tests executed
*Failed tests:*

Test results:
Console output:
Test logs:

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: 1 tests failed

This message is automatically generated.

ATTACHMENT ID: 12752154 - PreCommit-HIVE-TRUNK-Build

> ExprNodeDesc hashMap accidentally degrades into O(N) instead of O(1)
> --------------------------------------------------------------------
>                 Key: HIVE-11638
>                 URL:
>             Project: Hive
>          Issue Type: Improvement
>          Components: Logical Optimizer
>    Affects Versions: 0.14.0, 1.0.1, 1.1.1, 1.3.0, 1.2.1, 2.0.0
>            Reporter: Gopal V
>            Assignee: Gopal V
>              Labels: Performance
>         Attachments: HIVE-11638.1.patch
> Due to the absence of ExprNodeDesc::equals() & the presence of a hashCode(), any
code which computes a Set or HashMap of identical objects ends up with a skewed hashmap which
degrades column lookups from O(1) to O(N) during optimizer passes.
> So, several hundred references to a single column desc will be stored in a single hashbucket,
but since they default to Object::equals(), they are not equal to each other.
> Finalize the equals() method, so that the approach from HIVE-10215 carries over safely.

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