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Posted to dev@impala.apache.org by Gabor Kaszab <ga...@apache.org> on 2019/03/20 09:53:34 UTC

Introduce FORMAT clause to CAST with SQL:2016 datetime patterns

Hey Hive and Spark communities,
[dev@impala in cc]

I'm working on an Impala improvement to introduce the FORMAT clause within
CAST() operator and to implement ISO SQL:2016 datetime pattern support for
this new FORMAT clause:
https://issues.apache.org/jira/browse/IMPALA-4018

One example of the new format:
SELECT(CAST("2018-01-02 09:15" as timestamp FORMAT "YYYY-MM-DD HH12:MI"));

I have put together a document for my proposal of how to do this in Impala
and what patterns we plan to support to cover the SQL standard and what
additional patterns we propose to support on top of the standard's
recommendation.
https://docs.google.com/document/d/1V7k6-lrPGW7_uhqM-FhKl3QsxwCRy69v2KIxPsGjc1k/

The reason I share this with the Hive and Spark communities because I feel
it would be nice that these systems were in line with the Impala
implementation. So I'd like to involve these communities to the planning
phase of this task so that everyone can share their opinion about whether
this make sense in the proposed form.
Eventually I feel that each of these systems should have the SQL:2016
datetime format and I think it would be nice to have it with a newly
introduced CAST(..FORMAT..) clause.

I would like to ask members from both Hive and Spark to take a look at my
proposal and share their opinion from their own component's perspective. If
we get on the same page I'll eventually open Jiras to cover this
improvement for each mentioned systems.

Cheers,
Gabor

Re: Introduce FORMAT clause to CAST with SQL:2016 datetime patterns

Posted by Maciej Szymkiewicz <ms...@gmail.com>.

One concern here is introduction of second formatting convention.

This can not only cause confusion among users, but also result in some hard
to spot bugs, when wrong format, with different meaning, is used. This is
already a problem for Python and R users, with week year and months /
minutes mixups popping out from time to time.

On Wed, 20 Mar 2019 at 10:53, Gabor Kaszab <ga...@apache.org> wrote:

> Hey Hive and Spark communities,
> [dev@impala in cc]
>
> I'm working on an Impala improvement to introduce the FORMAT clause within
> CAST() operator and to implement ISO SQL:2016 datetime pattern support for
> this new FORMAT clause:
> https://issues.apache.org/jira/browse/IMPALA-4018
>
> One example of the new format:
> SELECT(CAST("2018-01-02 09:15" as timestamp FORMAT "YYYY-MM-DD HH12:MI"));
>
> I have put together a document for my proposal of how to do this in Impala
> and what patterns we plan to support to cover the SQL standard and what
> additional patterns we propose to support on top of the standard's
> recommendation.
>
> https://docs.google.com/document/d/1V7k6-lrPGW7_uhqM-FhKl3QsxwCRy69v2KIxPsGjc1k/
>
> The reason I share this with the Hive and Spark communities because I feel
> it would be nice that these systems were in line with the Impala
> implementation. So I'd like to involve these communities to the planning
> phase of this task so that everyone can share their opinion about whether
> this make sense in the proposed form.
> Eventually I feel that each of these systems should have the SQL:2016
> datetime format and I think it would be nice to have it with a newly
> introduced CAST(..FORMAT..) clause.
>
> I would like to ask members from both Hive and Spark to take a look at my
> proposal and share their opinion from their own component's perspective. If
> we get on the same page I'll eventually open Jiras to cover this
> improvement for each mentioned systems.
>
> Cheers,
> Gabor
>
>
>
>

-- 

Regards,
Maciej