How can I use datediff of postgresql with sequelizejs [duplicate] - postgresql

Question

I need to calculate DATEDIFF in minutes between 2 columns of timestamp type.
There are so many simple examples on the web, but none of them work really much properly using psycopg2 + sqlalchemy.
I've tried:
from sqlalchemy import as sa
from datetime import datetime
# con is a standard pool of connections :class:Connection
con.execute(
sa.func.datediff(
sa.literal_column('minute'),
datetime.utcnow(),
datetime.utcnow(),
)
)
it throws:
sqlalchemy.exc.ProgrammingError: (psycopg2.ProgrammingError) column "minute" does not exist
LINE 1: SELECT datediff(minute, '2017-02-27T15:04:33.217559'::timest...
^
[SQL: 'SELECT datediff(minute, %(datediff_2)s, %(datediff_3)s) AS datediff_1'] [parameters: {'datediff_3': datetime.datetime(2017, 2, 27, 15, 4, 33, 217596), 'datediff_2': datetime.datetime(2017, 2, 27, 15, 4, 33, 217559)}]
if I try:
con.execute(
sa.func.datediff(
'minute',
datetime.utcnow(),
datetime.utcnow(),
)
)
I receive:
sqlalchemy.exc.ProgrammingError: (psycopg2.ProgrammingError) function datediff(unknown, timestamp without time zone, timestamp without time zone) does not exist
LINE 1: SELECT datediff('minute', '2017-02-27T12:27:49.369724'::time...
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
[SQL: 'SELECT datediff(%(datediff_2)s, %(datediff_3)s, %(datediff_4)s) AS datediff_1'] [parameters: {'datediff_4': datetime.datetime(2017, 2, 27, 12, 27, 49, 369740), 'datediff_2': 'minute', 'datediff_3': datetime.datetime(2017, 2, 27, 12, 27, 49, 369724)}]
Any ideas how to make it right?

Answer 1

PostgreSQL does not have a datediff function. To get the number of minutes, use the SQL expression:
trunc((extract(epoch FROM newer_date) - extract(epoch FROM older_date)) / 60)
extract(epoch FROM …) converts the timestamp to number of seconds.
/ 60 converts to seconds to minutes
trunc(…) removes the fractional part.
So probably try
sa.func.trunc((
sa.extract('epoch', datetime.utcnow()) -
sa.extract('epoch', datetime.utcnow())
) / 60)