Also I fixed some bugs https://github.com/web2py/pydal/issues/548
пятница, 23 октября 2020 г. в 08:25:23 UTC+3, [email protected]: > > 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), >> ) >> >> -- Resources: - http://web2py.com - http://web2py.com/book (Documentation) - http://github.com/web2py/web2py (Source code) - https://code.google.com/p/web2py/issues/list (Report Issues) --- You received this message because you are subscribed to the Google Groups "web2py-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/web2py/c110dd27-35ea-4324-8ebe-c37580133a11n%40googlegroups.com.
