UP, never get any answer...
On Sat, Jan 23, 2016 at 4:08 PM, Val K <[email protected]> wrote:
> Hi guys!
> I have an idea to improve DAL in scope of work with normalized DB.
> As known It's a common practice to avoid NULL value by creating separate
> (option) table(s) to store non required fields.
> So, it would be great to have a field type like "storedin
> table_name.field_name"
> For example:
>
> db.define_table('alias_opt', Field('name'), Field('alias_name', 'reference
> person'))
> db.define_table('person', Field('name'), Field('alias_name', 'storedin
> alias_opt.alias_name'))
>
> #INSERT:
> db.person.insert(name='Alex', alias_name='Macedonian')
> # means:
> id=db.person.insert(name='Alex')
> db.alias_opt.insert(id=id, alias_name='Macedonian')
>
> #UPDATE:
> db(db.person.id==id).update(... , alias_name=None)
> # means:
> # update person
> ...
> # update option table
> update_opt_args = filter_storedin_fields(update_args)
> opt_rec = db.alias_opt(id)
> opt_rec.update(update_opt_args)
> if not any(opt_rec.values()): # - all fields of option table record is
> None
> del db.alias_opt(id)
> else:
> db.alias_opt.update_or_insert(id==id, **update_opt_args)
>
> #DELETE:
> del db.person(id) also means del db.alias_opt(id), like ondelete=
> 'CASCADE'
>
> #SELECT:
> rows = db(db.person).select()
> # means:
> rows = db(db.person).select( left=[ db.alias_opt.on( db.alias_opt.id ==
> db.person.id ) ] )
> but only "storedin" fields should be selected from db.alis_opt
> and they should be accessed by row.alias_name (not only by row.
> joined_table.field_name )
>
> Considering, that table person could be a VIEW (i.e. JOIN is already
> performed at DB level), there is no need to make join at web2py level,
> it could be fixed by passing an option arg like is_view=True to
> define_table()
> I know, that behavior of insert/update/delete could be easy realized by
> custom class based on Table
> with a little hacking Field-class to intercept field type to fix it to
> web2py type ( considering person.alias_name.type ==
> alias_opt.alias_name.type ).
> But it's hard for me to change select() behavior, because there is only
> common_filter, but there isn't common_join/common_left with providing of
> maping (aliasing) joined table fields to 'storedin' fields.
>
> In fact, I dream of common_join depends on discriminator field, that will
> switch tables to be joined depend on discriminator value specified in the
> query (something like db.object.type_id==type_id),
> if descriminator is not specified or couldn't be resolved at web2py level,
> it performs left join all tables (from a list containing possible
> common_join tables)
>
> P.S. May be I try to reinvent the wheel, so feel free to shoot me!
>
> --
> 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)
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--
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)
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