Thanks, that's a good thought. I agree that it should be done in a
transaction. However, I don't believe App Engine allows you to run
queries in a transaction.
Chris
2009/4/20 djidjadji <djidja...@gmail.com>:
>
> Hi Chris,
>
> You can do this by adding an extra attribute to the object that
> contains the date and a sequence number.
>
> The extra attribute is an IntegerProperty. It has arbitrary precision,
> unlimited bit length.
> If you store (long(datetime.toordinal(myRecord.date))<<128)+long(sequenceNum)
> you can store a lot of entities on one date, 2**128. If you set
> sequenceNum starting at 1 you can use your query that sets
>
> startDate = (long(datetime.toordinal(someDate1))<<128)+long(0)
> endDate = (long(datetime.toordinal(someDate2))<<128)+long(0)
> query = Record.all().filter('dateEx >', startDate).filter('dateEx <', endDate)
>
> if you fetch 100 objects use the value of dateEx of the last object
> retrieved as the new startDate for the next batch.
>
> When you store a new entity:
> get the object with the highest value of dateEx with the same
> ordinal value,
> add 1L and set as the dateEx value of the new entity
> This should be done in a transaction or some kind of "Critical
> section" to ensure unique sequence numbers
>
> 2009/4/20 Chris Spencer <chriss...@gmail.com>:
>>
>> Thanks, but I don't see how that's relevant. Like I said, the ordering
>> of an object's key has no correlation to an object's date.
>>
>> I'm not trying to simply page. That's trivial using the method listed
>> in your link. What I'm trying to do is page through a set of objects
>> limited by a date range.
>>
>> Chris
>>
>> 2009/4/19 秦锋 <feng.w....@gmail.com>:
>>>
>>> CHeck this:
>>> http://google-appengine.googlegroups.com/web/efficient_paging_using_key_instead_of_a_dedicated_unique_property.txt?gda=7FbhWXcAAACSStSWrftt07H4FK2Rtvurv5Qi9dmYyYZMEnTZCjCsYQQgER4RQV57mxjvIzAWBZmQ3TeCdbqm30Qz_AwgYlIpRbcWRj3jGGBm-fgbnPJIYc4-hXRRmo3Xgj6KgtSLBeZ45alvcyXc30EbEX-RNDZveV4duv6pDMGhhhZdjQlNAw
>>>
>>> On 4月19日, 下午12时32分, Chris <chriss...@gmail.com> wrote:
>>>> I have the model:
>>>>
>>>> class Record(db.Model):
>>>> date = db.DateProperty()
>>>>
>>>> Over 1000 Record instances may contain the same date value. The
>>>> instances are also not created in the order of their dates.
>>>>
>>>> I'm trying to query all instances whose date is within a given range.
>>>> I need to be able to query sets larger than the default max of 1000.
>>>>
>>>> I was thinking of doing something like:
>>>>
>>>> Record.all().filter('date >', startDate).filter('date <', endDate)
>>>>
>>>> But this would limit me at most to the first 1000 records. How would I
>>>> get the next 1000 records, maintaining the range query? I can't use
>>>> the last date value from the previous query as the startDate for the
>>>> next query, since there's no guarantee that the date value has
>>>> changed. For example, I could have 2000 instances with the date
>>>> 2008-1-1, so the first and second query sets have identical filter
>>>> parameters.
>>>>
>>>> Intuitively, I could accomplish this by simply filtering on the
>>>> previous key value (e.g. .filter('key >', lastKeyValue)).
>>>> Unfortunately, App Engine currently prohibits filtering with
>>>> inequality operators on more than one property.
>>>>
>>>> Am I correct in understanding that there's essentially no way to query
>>>> all instances within a specific date range, due to this limitation?
>>>>
>>>> This issue keeps coming up for me, and has been a huge deal-breaker in
>>>> a lot of potential projects I've been working on for App Engine. Any
>>>> advice on how I could work around it would be appreciated.
>>>>
>>>> Chris
>>> >
>>>
>
> >
>
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