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https://issues.apache.org/jira/browse/SPARK-17971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15583018#comment-15583018
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Sean Owen commented on SPARK-17971:
-----------------------------------
timestamps are not time-zone-specific (good) and any translation to
calendar-related representations must be done in the context of a specific
timezone. This must occur in the application code and not default to some
machine's setting. You need to use methods that take a timezone. See
https://spark.apache.org/docs/1.6.2/api/java/org/apache/spark/sql/functions.html#from_unixtime(org.apache.spark.sql.Column,%20java.lang.String)
> Unix timestamp handling in Spark SQL not allowing calculations on UTC times
> ---------------------------------------------------------------------------
>
> Key: SPARK-17971
> URL: https://issues.apache.org/jira/browse/SPARK-17971
> Project: Spark
> Issue Type: Bug
> Components: Spark Core, SQL
> Affects Versions: 1.6.2
> Environment: MacOS X JDK 7
> Reporter: Gabriele Del Prete
>
> In our Spark data pipeline we store timed events using a bigint column called
> 'timestamp', the values contained being Unix timestamp time points.
> Our datacenter servers Java VMs are all set up to start with timezone set to
> UTC, while developer's computers are all in the US Eastern timezone.
> Given how Spark SQL datetime functions work, it's impossible to do
> calculations (eg. extract and compare hours, year-month-date triplets) using
> UTC values:
> - from_unixtime takes a bigint unix timestamp and forces it to the computer's
> local timezone;
> - casting the bigint column to timestamp does the same (it converts it to the
> local timezone)
> - from_utc_timestamp works in the same way, the only difference being that it
> gets a string as input instead of a bigint.
> The result of all of this is that it's impossible to extract individual
> fields of a UTC timestamp, since all timestamp always get converted to the
> local timezone.
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