Good point. I suppose you can adapt your method to work with a virtual
field:
owners = {}
db.define_table('dog',
...
Field.Virtual('owner_record',
lambda r: owners.setdefault(r.dog.owner, db.person(r.dog.owner)))
That will store each fetched owner record in the owners dict, so the record
will be copied from the dict if it is already there rather than pulled from
the db.
Anthony
On Thursday, August 15, 2013 12:09:02 PM UTC-4, Quint wrote:
>
> But when when a row is calculating it's virtual field, it will fetch the
> referenced row even when some other row from the initial set has already
> fetched this same referenced row (when they are referencing the same
> thing). So they will both perform the same fetch.
>
> ?
>
> I want to do this fetch 1x and use that record for all rows from the
> initial set that reference it.
> On Aug 15, 2013 4:18 PM, "Anthony" <abas...@gmail.com <javascript:>>
> wrote:
>
>> On Thursday, August 15, 2013 10:04:45 AM UTC-4, Quint wrote:
>>
>>> thnx,
>>>
>>> but my goal is to prevent repeated queries for the same record when
>>> accessing ref fields on rows from the same result set.
>>>
>>> I'm missing something, how do those Virtual Fields achieve that?
>>>
>>
>> Yes, that's exactly what the virtual field does -- when the the Rows
>> object is created from the initial select, the value of the virtual field
>> is calculated for each Row, and it remains in the Row (i.e., it is not
>> re-calculated on each access). There is also Field.Method(), which does
>> re-calculate on every access (the advantage is that it is lazy, so nothing
>> is calculated until accessed -- and because of that, it can take arguments
>> at the time it is called).
>>
>> And about the join, wouldn't that mean it won't work on GAE?
>>>
>>
>> Oh, yeah, forgot you said you are on GAE.
>>
>> Anthony
>>
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