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https://issues.apache.org/jira/browse/DRILL-7926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17386505#comment-17386505
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ASF GitHub Bot commented on DRILL-7926:
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paul-rogers commented on pull request #2268:
URL: https://github.com/apache/drill/pull/2268#issuecomment-885875711
@dzamo, let's think a bit about your observation:
> You're using the UTC timezone when you work with left.value and
right.value and I think that's right.
As explained elsewhere, Drill defines its TIMESTAMP column as local time,
specifically, the number of ms. since 1970-01-01'T'00:00:00 *local time*. That
is, it is a ms offset, from a specific calendar date, but from midnight on that
date local time. This *looks* like UTC, but isn't. UTC is defined as ms. since
the epoch, and the epoch is UTC. Yes, I agree, this has long been *very*
confusing.
I find that writing words just gets folks further wrapped around the axle.
Tests, however, are unambiguous. If baby Fred's birthday is 2020-07-23, then
Fred's Age is 1 year (exactly) in any timezone, during the period from midnight
to midnight on 2021-07-23. Fred's age (as customarily stated) should not
include units finer than a day.
Drill's AGE function does return a finer grain: the number of ms:
> Returns the interval between two timestamps or subtracts a timestamp from
midnight of the current date.
This makes sense: it is the number of ms since midnight local time (since we
don't know, and wouldn't care about, the timezone in which Fred was born.)
And, the reason that the "midnight local time" makes sense is that even
TIMESTAMP are in local time.
Now, I could be wrong (we've seen cases where the code does one thing and
the documentation says another, or where two smart engineers strenuously
disagree about how Drill's time support is supposed to work.) So, *caveat
emptor*.
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> The " age " function is not working properly.
> ---------------------------------------------
>
> Key: DRILL-7926
> URL: https://issues.apache.org/jira/browse/DRILL-7926
> Project: Apache Drill
> Issue Type: Bug
> Components: Functions - Drill
> Affects Versions: 1.17.0, 1.18.0
> Reporter: Александр Глухов
> Priority: Blocker
> Attachments: image-2021-05-13-16-17-21-154.png, screenshot-1.png,
> screenshot-2.png
>
>
> The " age " function is not working properly.
> *Playback steps*
> {code:sql}
> select extract(year from m. "years") `years` from (select age('2021-05-13',
> '2007-07-02') `years") m{code}
> *Expected result* 13.
> *Actual result* 14.
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