Check this : http://d.hatena.ne.jp/ikasamaH/20080612
On 10 nov, 17:50, Kenchu <[EMAIL PROTECTED]> wrote: > Let's say I've got a model with a BlobProperty() holding data up to 2 > MB. Take this for example: > > class SomeDataFile(db.Model): > title = db.StringProperty() > data = db.BlobProperty() > > Now imagine I'd just want to fetch the title property for the items in > this model. if I'd query the model, then the datastore would fetch the > data property for every item. As far as I know, there's no way to ask > the datastore to select specific fields, making this query extremely > heavy since each data property would be fetched as well (which might > be 2 MB / item). > > I thought I might solve this by using another table for the actual > data, and then reference it in the SomeDataFile model as such: > > class Data(db.Model): > data = db.BlobProperty() > > class SomeDataFile(db.Model): > title = db.StringProperty() > data = db.ReferenceProperty(Data) > > But as it turns out, referenced items are included in the result > making it equally heavy. > > One solution might be to do this instead: > > class Data(db.Model): > data = db.BlobProperty() > > class SomeDataFile(db.Model): > title = db.StringProperty() > data = db.StringProperty() > > Where SomeDataFile.data is a string value of the key for the Data > item. But is that really a good solution? > > So the question is: > How do you NOT fetch a BlobProperty in a model (you want everything > but the Blob)? How would you model that? --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en -~----------~----~----~----~------~----~------~--~---
