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https://issues.apache.org/jira/browse/HIVE-21796?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Csaba Ringhofer updated HIVE-21796:
-----------------------------------
Attachment: HIVE-21796.2.patch
> ArrayWritableObjectInspector.equals can take O(2^nesting_depth) time
> --------------------------------------------------------------------
>
> Key: HIVE-21796
> URL: https://issues.apache.org/jira/browse/HIVE-21796
> Project: Hive
> Issue Type: Bug
> Reporter: Csaba Ringhofer
> Assignee: Csaba Ringhofer
> Priority: Major
> Attachments: HIVE-21796.1.patch, HIVE-21796.2.patch,
> HIVE-21796.patch, jstack.txt
>
>
> The issue came up during an Impala test when we tried to run it with Hive
> 3.1. The a query hanged: it tried to insert 1 row from a Parquet file with a
> 99 level nested column to a similar Orc file, and spent its time in
> ArrayWritableObjectInspector.equals() according to jstack.
> The problem seems to be that equals() calls both fields.equals(that.fields)
> and fieldsByName.equals(that.fieldsByName), and both try to compare all
> nested fields recursively, which leads to the O(2^nesting_depth) complexity.
> The commit that introduced this behavior:
> https://github.com/apache/hive/commit/98a25f2d831ab27e174bc99792047eaa8ec08b82#diff-8c6363e90d442f239bc252a104f1bfed
> The Impala test:
> https://github.com/apache/impala/blob/9ee4a5e1940afa47227a92e0f6fba6d4c9909f63/tests/query_test/test_nested_types.py#L612
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