Try something like this:
task_duration = (db.t_periods.f_end -
db.t_periods.f_start).sum().with_alias('task_duration')
results = db(query).select(db.t_tasks.f_name, task_duration,
groupby=db.t_tasks.f_name)
On Thursday, March 8, 2018 at 3:34:26 AM UTC-5, backseat wrote:
>
> OK, I know I can't get a sum of virtual fields, but here's what I'm trying
> to do:
>
> db.define_table(
> 't_periods',
> Field('f_start', type='datetime', label=T('Start time')),
> Field('f_end', type='datetime', label=T('End time')),
> Field('f_task', type='reference t_tasks', label=T('Task')),
>
> ...)
>
> db.t_periods.f_duration = Field.Virtual('f_duration',
> lambda row: row.f_end - row.
> f_start)
>
>
>
> So, for any one task there may be multiple periods of time. I would like a
> list of tasks and the total time allocated to each. I tried this:
>
> task_duration = db.t_periods.f_duration.sum()
>
> results = db(query).select(db.t_tasks.f_name, task_duration,
> groupby=db.t_tasks.f_name)
>
> That gives me the error:
>
> AttributeError: 'FieldVirtual' object has no attribute 'sum'
>
> That makes sense to me, but what would be a good strategy to get a list of
> tasks and the total duration for each?
>
> Thanks
>
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