On Dec 11, 12:41 am, Brian M <bmere...@gmail.com> wrote:
> t.staid could be the primary key as far as the database is concerned.
> The issue is that web2py expects the primary key field to be called
> ID.
>
> I'd give Massimo's suggestion of db.define_table(...Field
> ('staid','id'),...) a shot - he's the man, so he ought to know.
>
> Massimo - what exactly does Field('staid','id') do? Is that just
> telling web2py that field staid should be treated as the ID field? Is
> 'id' now a valid fieldtype just like 'string' or 'integer'?
This is probably another example where we would have benefitted from a
code review / design review.
"Field()" is constructor (manual, p.153), and used to define table
fields within the define_table constructor (the way that has been
web2py/DAL, in one form or another, "forever").
This is perhaps the first "special" form of "Field()", and the first
one to define default behavior of the "ID" field (which is why it is
natural at first blush to use the "Field()" constructor for this, but
as we see from this thread it is not intuitive, and can confuse by
virtue of a new, "special" form of a heretofore clear constructor).
define_table() has a special first parameter, which is the table name,
and an additional parameter which defines "special" table _behavior_,
that is "migrate=some_value".
Probably a better form for this particular change in default behavior
would have been something like: id='stiad'
Having an attribute of table called "id", once you look at the code,
shows all the places that the "magic field" (literal) "id" exists,
and should be replaced by an attribute (with default of id='id'; but
I digress...
I think, for define_table, a parameter of the form: id='staid'
would be both easier to explain (changes some default behavior of the
table, just as migrate does), more consistent with the historical
implementation, and at the same time would give the added benefit of
showing up a common, and problematic coding style w/in gluon of using
FNMs ("flaming magic numbers" - that is, a repetitive constant value
where a symboic value would make the code both more readable, and more
maintainable).
- Yarko
>
> ~Brian
>
> On Dec 10, 6:50 pm, Tim Michelsen <timmichel...@gmx-topmail.de> wrote:
>
>
>
> > > You can tell your model the path to the existing sqlite database file
> > > with something like
>
> > [...]
>
> > Thanks a lot for your verbose help! I really appreciate it.
>
> > > As for telling it which existing field to use as the ID, as DenesL
> > > pointed out if the field isn't already named ID I don't think you can
> > > at the moment.
>
> > > If you really want to use the station number (t.staid) as your ID, why
> > > not just add a new field called ID to your existing table (using
> > > sqlite-browser) and then set the value to match t.staid? Something
> > > like
>
> > I am not a database guru. So I still do not understand why t.staid could
> > not be the PK (= ID).
>
> > Regards,
> > Timmie
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