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https://issues.apache.org/jira/browse/HIVE-12192?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16522132#comment-16522132
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Matt McCline commented on HIVE-12192:
-------------------------------------
Reverted.
> Hive should carry out timestamp computations in UTC
> ---------------------------------------------------
>
> Key: HIVE-12192
> URL: https://issues.apache.org/jira/browse/HIVE-12192
> Project: Hive
> Issue Type: Sub-task
> Components: Hive
> Reporter: Ryan Blue
> Assignee: Jesus Camacho Rodriguez
> Priority: Blocker
> Labels: timestamp
> Fix For: 3.1.0
>
> Attachments: HIVE-12192.01.patch, HIVE-12192.02.patch,
> HIVE-12192.03.patch, HIVE-12192.04.patch, HIVE-12192.05.patch,
> HIVE-12192.06.patch, HIVE-12192.07.patch, HIVE-12192.08.patch,
> HIVE-12192.09.patch, HIVE-12192.10.patch, HIVE-12192.11.patch,
> HIVE-12192.12.patch, HIVE-12192.13.patch, HIVE-12192.14.patch,
> HIVE-12192.15.patch, HIVE-12192.16.patch, HIVE-12192.17.patch,
> HIVE-12192.18.patch, HIVE-12192.19.patch, HIVE-12192.20.patch,
> HIVE-12192.21.patch, HIVE-12192.22.patch, HIVE-12192.23.patch,
> HIVE-12192.24.patch, HIVE-12192.25.patch, HIVE-12192.patch
>
>
> Hive currently uses the "local" time of a java.sql.Timestamp to represent the
> SQL data type TIMESTAMP WITHOUT TIME ZONE. The purpose is to be able to use
> {{Timestamp#getYear()}} and similar methods to implement SQL functions like
> {{year}}.
> When the SQL session's time zone is a DST zone, such as America/Los_Angeles
> that alternates between PST and PDT, there are times that cannot be
> represented because the effective zone skips them.
> {code}
> hive> select TIMESTAMP '2015-03-08 02:10:00.101';
> 2015-03-08 03:10:00.101
> {code}
> Using UTC instead of the SQL session time zone as the underlying zone for a
> java.sql.Timestamp avoids this bug, while still returning correct values for
> {{getYear}} etc. Using UTC as the convenience representation (timestamp
> without time zone has no real zone) would make timestamp calculations more
> consistent and avoid similar problems in the future.
> Notably, this would break the {{unix_timestamp}} UDF that specifies the
> result is with respect to ["the default timezone and default
> locale"|https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF#LanguageManualUDF-DateFunctions].
> That function would need to be updated to use the
> {{System.getProperty("user.timezone")}} zone.
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