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Posted to issues@spark.apache.org by "Sean Owen (JIRA)" <ji...@apache.org> on 2018/08/26 13:39:00 UTC
[jira] [Assigned] (SPARK-23792) Documentation improvements for
datetime functions
[ https://issues.apache.org/jira/browse/SPARK-23792?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Sean Owen reassigned SPARK-23792:
---------------------------------
Assignee: A Bradbury
> Documentation improvements for datetime functions
> -------------------------------------------------
>
> Key: SPARK-23792
> URL: https://issues.apache.org/jira/browse/SPARK-23792
> Project: Spark
> Issue Type: Documentation
> Components: Documentation, SQL
> Affects Versions: 2.3.0
> Reporter: A Bradbury
> Assignee: A Bradbury
> Priority: Minor
> Fix For: 2.4.0
>
>
> Added details about the supported column input types, the column return type, behaviour on invalid input, supporting examples and clarifications to the datetime functions in `org.apache.spark.sql.functions` for Java/Scala.
> These changes stemmed from confusion over behaviour of the `date_add` method. On first use I thought it would add the specified days to the input timestamp, but it also truncated (cast) the input timestamp to a date, loosing the time part.
> Some examples:
> * Noted that the week definition for `dayofweek` method starts on a Sunday
> * Corrected documentation for methods such as `last_day` that only listed one type of input i.e. "date column" changed to "date, timestamp or string"
> * Renamed the parameters of the `months_between` method to match those of the `datediff` method and to indicate which parameter is expected to be before then other chronologically
> * `from_unixtime` documentation referenced the "given format" when there was no format parameter
> * Documentation for `to_timestamp` methods detailed that a unix timestamp in seconds would be returned (implying 1521926327) when they would actually return the input cast to a timestamp type
> Some observations:
> * The first day of the week by the `dayofweek` method is a Sunday, but by the `weekofyear` method it is a Monday
> * The `datediff` method returns a integer value, even with timestamp input, whereas the `months_between` method returns a double, which seems inconsistent
>
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