Netezza In-Built AGE function as UDF in Redshift

Question

I'm trying to Implement Netezza AGE function in Redshift as a UDF. I can able to get the correct answer in Python (Spyder IDE - Py 3.6) but when I execute it in Redshift as UDF, it gives me incorrect output.

I've tried to execute as select AGE_UDF('1994-04-04 20:10:52','2018-09-24 11:31:05'); in Redshift. Here is the code used in RS UDF.

CREATE OR REPLACE FUNCTION AGE_UDF (START_DATE TIMESTAMP, END_DATE TIMESTAMP)
    RETURNS varchar(100)
stable
AS $$
    from datetime import datetime
    from dateutil import relativedelta

    START_DATE = datetime.strptime(START_DATE, '%Y-%m-%d %H:%M:%S')

    END_DATE = datetime.strptime(END_DATE, '%Y-%m-%d %H:%M:%S')

    difference = relativedelta.relativedelta(END_DATE, START_DATE)

    years = difference.years
    months = difference.months
    days = difference.days
    hours = difference.hours
    minutes = difference.minutes
    seconds = difference.seconds
    age=''
    if years == 0: 
        age='' 
    elif years == 1:
        age+=str(years)+' year '
    else:
        age+=str(years)+' years '

    if months == 0: 
        age+='' 
    elif months == 1:
        age+=str(months)+' mon '
    else:
        age+=str(months)+' mons '

    if days == 0: 
        age+='' 
    elif days == 1:
        age+=str(days)+' day '
    else:
        age+=str(days)+' days '

    age+=str(hours)+':'+str(minutes)+':'+str(seconds)
    return age
$$ language plpythonu;

Output in RS: -8809.15:20:13

Here is the Code used in Python (3.6).

from datetime import datetime
from dateutil import relativedelta

START_DATE = '1994-04-04 20:10:52'
START_DATE = datetime.strptime(START_DATE, '%Y-%m-%d %H:%M:%S')

END_DATE = '2018-09-24 11:31:05'
END_DATE = datetime.strptime(END_DATE, '%Y-%m-%d %H:%M:%S')

difference = relativedelta.relativedelta(END_DATE, START_DATE)

years = difference.years
months = difference.months
days = difference.days
hours = difference.hours
minutes = difference.minutes
seconds = difference.seconds
age=''
if years == 0: 
    age='' 
elif years == 1:
    age+=str(years)+' year '
else:
    age+=str(years)+' years '


if months == 0: 
    age+='' 
elif months == 1:
    age+=str(months)+' mon '
else:
    age+=str(months)+' mons '


if days == 0: 
    age+='' 
elif days == 1:
    age+=str(days)+' day '
else:
    age+=str(days)+' days '

age+=str(hours)+':'+str(minutes)+':'+str(seconds)
print(age)

Output in Python: 24 years 5 mons 19 days 15:20:13

EDIT:

I found the way to achieve the Netezza functionality and I've pasted here. Still I'm Expecting an another efficient way !!! Cheers !!!

Thanks for the Support and Suggestions !!!

Answer 1

I Found the way to get the output as same as Netezza ! And we need to create 4 Different UDF with different Inputs ! Here I've added the UDF for (TIMESTAMP, TIMESTAMP)

create or replace function AGE_UDF_V2 (START_DATE TIMESTAMP, END_DATE TIMESTAMP)
  returns VARCHAR
stable
as $$
# -*- coding: utf-8 -*-
"""
Created on Wed Sep 26 12:59:24 2018

@author: pnataraj
"""

from dateutil import relativedelta
from dateutil.parser import parse

if (START_DATE is None or END_DATE is None):
    return None

else:
    START_DATE = str(START_DATE).strip()
    END_DATE = str(END_DATE).strip()

    START_DATE = parse(START_DATE)
    END_DATE = parse(END_DATE)

    difference = relativedelta.relativedelta(START_DATE, END_DATE)
    years = difference.years
    months = difference.months
    days = difference.days
    hours = difference.hours
    minutes = difference.minutes
    seconds = difference.seconds
    age=''
    if years != 0:
        if years == 1 or years == -1:
            age+=str(years)+' year '
        else:
            age+=str(years)+' years '

    if months != 0:
        if months == 1 or months == -1:
            age+=str(months)+' mon '
        else:
            age+=str(months)+' mons '

    if days != 0: 
        if days == 1 or days == -1:
            age+=str(days)+' day '
        else:
            age+=str(days)+' days '

    if (hours !=0 or minutes !=0 or seconds != 0):
        if (hours < 0 or minutes < 0 or seconds < 0):
            age+=str("-"+format(abs(hours),"02")+":"+format(abs(minutes),"02")+":"+format(abs(seconds),"02"))
        else:
            age+=str(format(hours,"02")+":"+format(minutes,"02")+":"+format(seconds,"02"))
    elif(hours == 0 and minutes ==0 and seconds == 0):
        if len(age)>0:
            age = age
        else:
            age = "00:00:00"

    return age.strip()
$$ language plpythonu;

Thanks for all the suggestions and Helps ! Hope It'll be helpful for those who're doing Nz to AWS RS Migration !

Answer 2

No Python needed. Here's a SQL UDF that encapsulates the logic. You will need to extend it if the units plural is important to you (mons vs mon).

/*
    Postgres AGE() Function
*/
CREATE OR REPLACE FUNCTION f_postgres_age(TIMESTAMP, TIMESTAMP) 
RETURNS VARCHAR(64) 
STABLE AS $$
-- Input: '1994-04-04 20:10:52', '2018-09-24 11:31:05' 
-- Output: 24 years 5 mons 19 days 15:20:13
-- Input: '1994-10-04 20:10:52', '2019-06-12 11:31:05' 
-- Output: 24 years 8 mons 7 days 15:20:13
-- Check: SELECT '1994-10-04 20:10:52'::TIMESTAMP 
--               + INTERVAL '24 years' + INTERVAL '8 months' + INTERVAL '7 days'
--               + INTERVAL '15 hours' + INTERVAL '20 minutes' + INTERVAL '13 seconds';
-- Result: 2019-06-12 11:31:05
SELECT CASE WHEN DATEDIFF(year, DATE_TRUNC('year', $1)
                              , DATE_TRUNC('year', CASE WHEN DATEPART(month, $1) > DATEPART(month, $2)
                                                        THEN $2 - INTERVAL '1 Year' ELSE $2 END)) > 0
            THEN DATEDIFF(year, DATE_TRUNC('year', $1)
                              , DATE_TRUNC('year', CASE WHEN DATEPART(month, $1) > DATEPART(month, $2)
                                                        THEN $2 - INTERVAL '1 Year' ELSE $2 END)) || ' years '
       ELSE '' END
    || CASE WHEN ABS(  DATEDIFF(month, DATE_TRUNC('month', $1), DATE_TRUNC('month', $2))
                     - DATEDIFF(month, DATE_TRUNC('year', $1)
                                     , DATE_TRUNC('year', CASE WHEN DATEPART(month, $1) > DATEPART(month, $2)
                                                               THEN $2 - INTERVAL '1 Year' ELSE $2 END))) > 0
            THEN DATEDIFF(month, DATE_TRUNC('month', $1), DATE_TRUNC('month', $2))
               - DATEDIFF(month, DATE_TRUNC('year', $1)
                               , DATE_TRUNC('year', CASE WHEN DATEPART(month, $1) > DATEPART(month, $2)
                                                         THEN $2 - INTERVAL '1 Year' ELSE $2 END)) || ' mons '
       ELSE '' END
    || CASE WHEN ABS( DATEDIFF(day, DATE_TRUNC('day', $1)+1, DATE_TRUNC('day', $2)) 
                    - DATEDIFF(day, DATE_TRUNC('month', $1), DATE_TRUNC('month', $2))) > 0
            THEN DATEDIFF(day, DATE_TRUNC('day', $1)+1, DATE_TRUNC('day', $2))
               - DATEDIFF(day, DATE_TRUNC('month', $1), DATE_TRUNC('month', $2)) || ' days '
       ELSE '' END
    || TO_CHAR((TIMESTAMP 'epoch' 
                + ( DATEDIFF(second, $1, DATE_TRUNC('day', $1)+1 )
                  + DATEDIFF(second, DATE_TRUNC('day', $2), $2) )
                * INTERVAL '1 Second '),'HH24:MI:SS') age
$$ LANGUAGE SQL
;