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https://issues.apache.org/jira/browse/IMPALA-8241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16780278#comment-16780278
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Quanlong Huang commented on IMPALA-8241:
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[~attilaj] [~tarmstrong], thanks for your clarification! I think this is rather
a bug of Hive.
I struggled to understand the behavior of Hive's from_utc_timestamp UDF. It's
quite a mess that it has different meanings for different parameter types due
to the implicit cast in Hive. The most reasonable case is when the parameter is
STRING. Comparing to Hive, Impala's semantic is quite friendly and
understandable.
Our analysts just want to convert a column of unix timestamps in BIGINT to a
column of time STRING in New York time zone, while the machine is in Los
Angeles time zone. They can use
{code:java}
impala> select from_utc_timestamp(cast(0 as timestamp), 'America/New_York');
{code}
in Impala to get what they want. However, to achieve the same functionality in
Hive, they should run in the following wired way...
{code:java}
hive> select to_utc_timestamp(from_utc_timestamp(0, 'America/New_York'),
'America/Los_Angeles');{code}
> from_utc_timestamp returns inconsistent results with Hive
> ---------------------------------------------------------
>
> Key: IMPALA-8241
> URL: https://issues.apache.org/jira/browse/IMPALA-8241
> Project: IMPALA
> Issue Type: Bug
> Reporter: Quanlong Huang
> Priority: Major
>
> This can be reproduced in both master and 2.x branches.
> {code}
> [localhost:21000] default> select from_utc_timestamp(cast(400000 * 3600.0 as
> timestamp), 'EST');
> Query: select from_utc_timestamp(cast(400000 * 3600.0 as timestamp), 'EST')
> Query submitted at: 2019-02-23 17:27:02 (Coordinator:
> http://impala-jenkins-slave-02:25000)
> Query progress can be monitored at:
> http://impala-jenkins-slave-02:25000/query_plan?query_id=f476c87a904f281:71588a2400000000
> +---------------------------------------------------------------+
> | from_utc_timestamp(cast(400000 * 3600.0 as timestamp), 'est') |
> +---------------------------------------------------------------+
> | 2015-08-19 11:00:00 |
> +---------------------------------------------------------------+
> Fetched 1 row(s) in 0.64s
> {code}
> {code}
> hive> select from_utc_timestamp(cast(400000 * 3600.0 as timestamp), 'EST');
> OK
> 2015-08-19 04:00:00
> {code}
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