I went with:
query = ''
for id in board_ids:
query += 'db(db.board.id==%d).select()|' %id
query = query[:-1]
boards = eval(query)
I have no idea how to evaluate performance of that query though....
if you have any other ideas (I cannot limit 30 right now without rethinking
other things), please share them.
On Wednesday, March 21, 2012 11:52:33 PM UTC-4, Anthony wrote:
>
> I think that is outdated -- according to this (
> https://groups.google.com/d/msg/web2py/vWqOET74qg4/92DLUFTUsN0J), GAE
> does now support belongs but is limited to 30 items per query (so you have
> to break it up). Perhaps there is a better way, though.
>
> Anthony
>
> On Wednesday, March 21, 2012 9:26:44 PM UTC-4, Udi Milo wrote:
>>
>> 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
>>>>>
>>>>>
