Jesus Camacho Rodriguez updated HIVE-12192:
    Attachment: HIVE-12192.03.patch

> 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: Major
>              Labels: timestamp
>         Attachments: HIVE-12192.01.patch, HIVE-12192.02.patch, 
> HIVE-12192.03.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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