Thread: [BUGS] BUG #14850: Implement optinal additinal parameter for 'justify'date/time function

The following bug has been logged on the website:

Bug reference:      14850
Logged by:          Eugen Konkov
Email address:      kes-kes@yandex.ru
PostgreSQL version: 10.0
Operating system:   Linux mint 18: Linux work 4.4.0-57-generic #78-Ubu
Description:

Hi. I try to do next math:

select extract( month from justify_days( timestamp '2016-01-31' +interval '1
month' -timestamp '2016-01-31') );date_part 
-----------        0
(1 row)

I expect `1` but get `0`. But here everything is right:

>Adjust interval so 30-day time periods are represented as months

https://www.postgresql.org/docs/9.6/static/functions-datetime.html

But with ability to setup justify date the math will be more sharp.

Please implement next feature:

select extract( month from justify_days( timestamp '2016-01-31' +interval '1
month' -timestamp '2016-01-31'), timestamp '2016-01-31' );date_part 
-----------        1
(1 row)

This is useful when I try to calculate how much month are left between
service start and end dates.

Thank you.


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On Wed, Oct 11, 2017 at 10:35:12AM +0000, kes-kes@yandex.ru wrote:
> 
> >Adjust interval so 30-day time periods are represented as months
> 
> https://www.postgresql.org/docs/9.6/static/functions-datetime.html
> 

Yes, it seems that it is because timestamp operations return '29 days':

=# SELECT timestamp '2016-01-31' +interval '1 month' -timestamp '2016-01-31';?column?
----------29 days

You can also try the following, maybe it is appropriate for you:

=# SELECT timestamp '2016-01-31' -timestamp '2016-01-31' +interval '1 month';?column?
----------1 mon

=# SELECT extract( month from justify_days( timestamp '2016-01-31' 
-timestamp '2016-01-31' +interval '1 month') );date_part
-----------        1

-- 
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company


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No. Your example work only for those values.

Try this:
SELECT extract( month from justify_days( timestamp '2016-02-29' -timestamp '2016-01-31') );date_part 
-----------        0
(1 row)

select extract( month from justify_days( timestamp '2016-02-29' -timestamp '2016-01-31'), timestamp '2016-01-31'
);date_part
-----------        1
(1 row)

12.10.2017, 12:15, "Arthur Zakirov" <a.zakirov@postgrespro.ru>:
> On Wed, Oct 11, 2017 at 10:35:12AM +0000, kes-kes@yandex.ru wrote:
>>  >Adjust interval so 30-day time periods are represented as months
>>
>>  https://www.postgresql.org/docs/9.6/static/functions-datetime.html
>
> Yes, it seems that it is because timestamp operations return '29 days':
>
> =# SELECT timestamp '2016-01-31' +interval '1 month' -timestamp '2016-01-31';
>  ?column?
> ----------
>  29 days
>
> You can also try the following, maybe it is appropriate for you:
>
> =# SELECT timestamp '2016-01-31' -timestamp '2016-01-31' +interval '1 month';
>  ?column?
> ----------
>  1 mon
>
> =# SELECT extract( month from justify_days( timestamp '2016-01-31'
> -timestamp '2016-01-31' +interval '1 month') );
>  date_part
> -----------
>          1
>
> --
> Arthur Zakirov
> Postgres Professional: http://www.postgrespro.com
> Russian Postgres Company


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