you're right.
the "query" actually is only the "where" part, and if you serialize that as
a string it loses other attributes necessary to construct the other parts
of the query.
Now, I don't understand why this is a problem: you can:
- cache the results without hitting the database twice using the cache
argument of the select
- display technically what query produced that results, you can use the
._select() ....
- save the query and then retrieve the results you can, the only caveat is
having the condition linking the tables "alive" and not serialized....
linkwebpage2comment = (db.comment.page_id == db.webpage.id)
cond = (db.comment.id > 0) & (db.webpage.title == 'FAQ')
print cond
print 'a'
print db(linkwebpage2comment)(cond)._select(db.comment.body)
print 'b'
cond = str(cond)
print db(linkwebpage2comment)(cond)._select(db.comment.body)
- serialize full query with the _select() and then retrieve results with
executesql()
I'm just missing the point: is this functionality really a limit to your
application ?
Il giorno martedì 27 marzo 2012 01:38:32 UTC+2, Limedrop ha scritto:
>
> Hi Niphlod,
>
> Thanks for your reply. I'm running 1.99.7 and here's the model:
>
> db.define_table('webpage',
> Field('title'),
> Field('body', 'text'))
>
> db.define_table('comment',
> Field('page_id', db.webpage),
> Field('body', 'text'))
>
> The issue is when you have an implicit inner join, but where you only
> want one table in the output.
> I've found a thread where Massimo says that support for stings in
> queries is "clanky" and that
> you need a db(db.table) or db(db.table.field) to determine which table
> is needed.
>
> http://groups.google.com/group/web2py/browse_thread/thread/2024f660a8981558/d4b0e90d701833bb
>
>
> So I guess it isn't supported?
>
>
> On Mar 27, 12:15 am, Niphlod <[email protected]> wrote:
> > damn mobile phone screen....
> > I got it, seems a simple join, and for my simple model works without a
> > hitch.
> >
> > can you please post your model and tell what web2py version are you
> running
> > ?
> >
> > Il giorno lunedì 26 marzo 2012 01:58:31 UTC+2, Limedrop ha scritto:
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > > The difference is in the FROM clause. In the second SQL the webpage
> > > table is missing.
> >
> > > On Mar 26, 12:51 pm, Niphlod <[email protected]> wrote:
> > > > is that because of the "extra" () ?
> > > > every time you call db() the where clause gets "encapsulated" in a
> pair
> > > of
> > > > parenthesis.
> >
> > > > db(db.auth_user.id>0)(db.auth_user.email==localhost)
> >
> > > > and
> >
> > > > db((db.auth_user.id>0) & (db.auth_user.email==localhost))
> >
> > > > give you different raw strings, but the same exact result.
> >
> > > > Il giorno sabato 24 marzo 2012 21:49:58 UTC+1, Limedrop ha scritto:
> >
> > > > > I've copied this from the bottom of another thread.
> >
> > > > > The DAL gives different SQL when a query is provided in string
> format.
> > > > > Is this a bug, or should I not expect this to work?
> >
> > > > > See the example below, the first SQL works, the second SQL raises
> an
> > > > > error.
> >
> > > > > >>>from gluon.dal import Query
> > > > > >>>query = (db.comment.id > 0) & (db.webpage.title == 'FAQ') &
> > > > > (db.comment.page_id == db.webpage.id)
> > > > > >>>query_as_string = str(query)
> > > > > >>>query_from_string = Query(db, query_as_string)
> > > > > >>>print db(query)._select(db.comment.body)
> >
> > > > > SELECT comment.body FROM comment, webpage WHERE (((comment.id >
> 0)
> > > > > AND (webpage.title = 'FAQ')) AND (comment.page_id = webpage.id));
> >
> > > > > >>>print db(query_from_string)._select(db.comment.body)
> >
> > > > > SELECT comment.body FROM comment WHERE ((((comment.id > 0) AND
> > > > > (webpage.title = 'FAQ')) AND (comment.page_id = webpage.id)));
> >
> > > > > Why do this? If the were possible it would enable you to easily
> save
> > > > > a query in the session. For example:
> >
> > > > > ==Controller 1==
> > > > > query1 = (db.comment.id > 0) & (db.webpage.title == 'FAQ') &
> > > > > (db.comment.page_id == db.webpage.id)
> > > > > session.query = str(query1)
> >
> > > > > ==Controller 2==
> > > > > from gluon.dal import Query
> > > > > query2 = Query(db, session.query)
> >
> > > > > This does NOT work because the DAL gives different SQL for query1
> and
> > > > > query2.
