id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
24699	Add Avg('DurationField') support on Oracle	Tim Graham	Josh Smeaton	"From Josh in a [https://github.com/django/django/pull/4548 PR]:

Oracle doesn't allow `Avg` or `Sum` on interval data types. Seems like the commonly accepted way to do so is with `EXTRACT(day from 24*60*60*interval)`. See http://stackoverflow.com/a/5063553/10583. That only gets you to second resolution though, completely ignoring microseconds. Not really ideal.

http://www.dba-oracle.com/t_timestamp_math_elapsed_times.htm is another option which involves extracting each piece of the date component and multiplying by a constant. That'll give microsecond precision (decimal second component at least).
{{{
with the_interval as (
  select INTERVAL '4 5:12:10.999999' DAY TO SECOND(6) itv from dual
)
select 
  itv,
 -- convert back to interval after applying avg function
 NUMTODSINTERVAL(avg(extract(day from itv)*86400 +
  extract(hour from itv)*3600 +
  extract(minute from itv)*60 +
  extract(second from itv)), 'SECOND') seconds_with_precision,
  extract(day from 24*60*60*itv) seconds_without_precision
from the_interval;
}}}

To support this in `AVG`, we'd need to create an `as_oracle()` method, test if the `output_field` is an interval, and then wrap `output_field` with multiple extracts. The `functions.Coalesce` does something similar with `TextField`s, so it's not unprecedented."	New feature	closed	Database layer (models, ORM)	dev	Normal	fixed	oracle		Ready for checkin	1	0	0	0	0	0