It doesn't.
I found this:
""""
GAE does not support belongs and does not support OR. You have to do:
rows = db(db.media_type.name=='paper').select()&db
(db.media_type.name=='cd').select()
The & is done at the web2py level but since records are exclusive and
you are not sorting them, there is no major slowdown.
"""""
Since I'm a python newbie, how would you go about building the loop that
creates a very long query? you need to do some kind of python eval tricks
here that I don't know.
I'm guessing its going to look like
for id in board_ids:
query = query + new query(id)
but how do you do it in python?
On Wednesday, March 21, 2012 8:30:54 PM UTC-4, Anthony wrote:
>
> I didn't realize you were on GAE. I'm not quite sure how GAE handles this,
> so perhaps someone with more GAE experience can chime in. In an RDBMS, you
> should be able to do:
>
> board_ids = set([a.board for a in articles])
> boards = db(db.boards.id.belongs(board_ids)).select()
>
> But not sure if that works on GAE.
>
> Anthony
>
> On Wednesday, March 21, 2012 7:30:58 PM UTC-4, Udi Milo wrote:
>>
>> Anthony,
>>
>> Thanks for answering so quickly.
>> I did mean board and not board_id
>>
>> My question is very basic.
>> I know that the article table has an Id column that is really the board
>> reference, but when I look at the result of the query and unification of:
>> board_ids = set(map(lambda a: a.board, articles))
>>
>> I get a set of references,
>> how do I use that set in another query to get all the boards?
>> also, just to be sure, running this lambda expression does not hit the db
>> to fetch the boards, right?
>>
>> I can't use join b/c I'm running on GAE.
>>
>>
>>
>> On Wednesday, March 21, 2012 5:22:50 PM UTC-4, Anthony wrote:
>>>
>>> I have two db tables:
>>>>
>>>> board (name, created_on)
>>>> article(board, name, title)
>>>>
>>>> currently, in my html I do a naive loop {{for article in articles}} {{=
>>>> article.board.name}} {{pass}}
>>>>
>>>> I would like to change it and do something like:
>>>> articles = db.select.all.......
>>>> board_ids = set(map(lambda a: a.board_id, articles))
>>>>
>>>
>>> Instead of a.board_id, do you mean a.board (I don't see a "board_id"
>>> field listed in your article table definition)? Also, is db.article.board a
>>> reference field to the db.board table? In that case, that means it is
>>> already storing the id of the referenced record in the db.board table
>>> (that's what reference fields store), so you don't need to retrieve it
>>> separately.
>>>
>>> Anyway, if you need the db.board.name value for all the records you are
>>> selecting from the db.article table, you should probably just do a join so
>>> you can get everything in a single query -- see
>>> http://web2py.com/books/default/chapter/29/6#Inner-joins.
>>>
>>> Anthony
>>>
>>>
