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https://issues.apache.org/jira/browse/HIVE-18304?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16297824#comment-16297824
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Hengyu Dai commented on HIVE-18304:
-----------------------------------
SimpleDateFormat.parse(String source) method will convert String type(UTC) to
java.util.Date type(use current JVM timezone), this may lead deviations in time
when JVM timezone is not UTC, my environment is GMT+8, 8 hours is added
comparing to the UTC time.
while for a date type argument, the default JVM timezone is used.
The patch uploaded treats String type and Date type at the same way to remove
the deviations.
> datediff() UDF returns a wrong result when dealing with a (date, string) input
> ------------------------------------------------------------------------------
>
> Key: HIVE-18304
> URL: https://issues.apache.org/jira/browse/HIVE-18304
> Project: Hive
> Issue Type: Bug
> Components: UDF
> Reporter: Hengyu Dai
> Assignee: Hengyu Dai
> Priority: Minor
> Attachments: 0001.patch
>
>
> for date type argument, datediff() use DateConverter to convert input to a
> java Date object,
> for example, a '2017-12-18' will get 2017-12-18T00:00:00.000+0800
> for string type argument, datediff() use TextConverter to convert a string to
> date,
> for '2012-01-01' we will get 2012-01-01T08:00:00.000+0800
> now, datediff() will return a number less than the real date diff
> we should use TextConverter to deal with date input too.
> reproduce:
> {code:java}
> select datediff(cast('2017-12-18' as date), '2012-01-01'); --2177
> select datediff('2017-12-18', '2012-01-01'); --2178
> {code}
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