Presto SQL date_format extract week of year - sql

Question

Documentation : https://prestodb.io/docs/current/functions/datetime.html
I have epoch timestamps from which I want to extract week of the year like 2021-32, 2020-50, 2021-02 and so on.
SELECT concat(date_format(from_unixtime((CAST(my_timestamp AS BIGINT) + 19800000)/1000), '%Y'),
'-' ,
date_format(from_unixtime((CAST(my_timestamp AS BIGINT) + 19800000)/1000), '%v'))
AS week
However I am getting up some wrong values like :
week = 2021-53 for Epoch-Time corresponding to Jan 1, 2021 or Jan 2, 2021. I understand that there is a sync issue happening here but that is definitely not something I want - How do I offset so that first day of week 1 starts from the beginning of the year.

Answer 1

In that case you should just get the count of days and calculate the week.
Something like this:
SELECT concat(date_format(from_unixtime((CAST(my_timestamp AS BIGINT) + 19800000)/1000), '%Y'),
'-' ,
ceiling(date_format(from_unixtime((CAST(my_timestamp AS BIGINT) + 19800000)/1000), '%j')/7))
AS week

Answer 2

I was able to solve it using week_of_year and year_of_week methods.
Docs : https://prestodb.io/docs/current/functions/datetime.html#week
Query :
SELECT concat(CAST(year_of_week(from_unixtime((CAST(my_timestamp AS BIGINT) + 19800000)/1000)) AS varchar(15)),
'-',
CAST(week_of_year(from_unixtime((CAST(my_timestamp AS BIGINT) + 19800000)/1000)) AS varchar(15))) as week
Had to introduce some extra casts to varchar since concat doesn't support multiple datatypes.
Edit :
Another issue with above solution is that week_of_year returns single-digit weeks like 1, 2 instead of 01, 02 - thus causing an issue while sorting with these week numbers.
I ended up using a combination of year_of_week to get the correct year, and the general date_format(date, '%v') for week-numbers.
Updated Query :
SELECT concat(CAST(year_of_week(from_unixtime((CAST(my_timestamp AS BIGINT) + 19800000)/1000)) AS varchar(15)),
'-',
date_format(from_unixtime((CAST(my_timestamp AS BIGINT) + 19800000)/1000), '%v'))

Answer 3

There is no sync issue here - it expected behaviour for date_format and it's MySQL counterpart.
Note, that you can use full format string on the date:
select date_format(timestamp '2021-01-01', '%Y-%v')
_col0
2021-53
You can try calculating week number by dividing day_of_year by 7:
select ceiling(day_of_year(timestamp '2021-01-01') / 7.0)
Related:
presto github issue
joda weekOfWeekyear docs