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https://issues.apache.org/jira/browse/FLINK-7735?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16189918#comment-16189918
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Kent Murra commented on FLINK-7735:
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IMO using Java 8 time after Java 7 is officially dropped would be ideal.
> Improve date/time handling in publically-facing Expressions
> -----------------------------------------------------------
>
> Key: FLINK-7735
> URL: https://issues.apache.org/jira/browse/FLINK-7735
> Project: Flink
> Issue Type: Wish
> Components: Table API & SQL
> Reporter: Kent Murra
> Priority: Minor
>
> I would like to discuss potential improvements to date/time/timestamp
> handling in Expressions. Since Flink now offers expression push down for
> table sources, which includes time-related functions, timezone handling is
> more visible to the end user.
> I think that the current usage of java.sql.Time, java.sql.Date, and
> java.sql.Timestamp are fairly ambiguous. We're taking a Date subclass in the
> constructor of Literal, and assuming that the year, month, day, and hour
> fields apply to UTC rather than the user's default timezone. Per that
> assumption, Flink is [adjusting the value of the epoch
> timestamp|https://github.com/apache/flink/blob/master/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/expressions/literals.scala#L106]
> silently when converting to the RexLiteral. This provides correct behavior
> if the user assumes that the year/month/day/hour fields in the Date object
> are the same timezone that the SQL statement assumes (which is UTC).
> However, if they work at all with the epoch timestamp (which is a public
> field) this can lead to incorrect results. Moreover, its confusing if you're
> considering the time zones your data is in, requiring some amount of research
> to determine correct behavior.
> It would be ideal to:
> # Provide primitives that have time-zone information associated by default,
> thus disambiguating the times.
> # Properly document all TimeZone related assumptions in Expression literals.
> # Document that the TIMESTAMP calcite function will assume that the timestamp
> is in UTC in web documentation.
> # Having a timezone based date parsing function in the SQL language.
> Regarding the primitives, since we have to support Java 7, we can't use Java
> 8 time API. I'm guessing it'd be a decision between using Joda Time or
> making thin data structures that could easily be converted to various other
> time primitives.
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