Shared pk works just fine:
db.define_table(
'datetime_duration',
Field('superclass','reference duration') ,
primarykey = ['superclass']
)
воскресенье, 18 октября 2020 г. в 02:23:00 UTC+3, BigBaaadBob:
> It's hard to believe that I was talking about this in 2013
> <https://groups.google.com/g/web2py/c/Vh-J2AQ-mBE/m/xOMh3mm7ovEJ>, but
> here it is again!
>
> I'm wondering if you can directly implement the Table-per-type or
> Shared-primary-key method of inheritance in the DAL?
>
> [image: subclass-gradstu-scheme.gif]
>
> The standard DAL inheritance method (including a table as a field) is a
> Table-per-concrete approach that has pros and cons. In particular for me,
> it is harder to deal with the common stuff (the stuff in the superclass)
> with the standard DAL method. In many cases I never need to refer to the
> subclass specifics.
>
> The best I have been able to do is something like the below. There is a
> lot of common stuff in the duration table (and, btw, the duration can be
> overridden and isn't necessarily the difference of the start and stop
> values in the subclasses). Depending on how the time is tracked, there are
> different algorithms used to compute a duration, for example subtracting
> two datetimes or subtracting two floats (representing hours).
>
> db.define_table(
> 'duration',
> # Common stuff
> Field('duration','decimal(10,2)',notnull=True),
> )
>
> db.define_table(
> 'datetime_duration',
> Field('superclass','reference duration',unique=True,notnull=True),
> Field('start','datetime',notnull=True),
> Field('stop','datetime',notnull=True),
> )
>
> db.define_table(
> 'hour_duration',
> Field('superclass','reference duration',unique=True,notnull=True),
> Field('start','decimal(10,2)',notnull=True),
> Field('stop','decimal(10,2)',notnull=True),
> )
>
>
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