You should balance the needs of querying for children against updating the parent - if you are checking for the lack of children much more than you are actually updating parents, it will be way cheaper to implement a boolean that denotes whether or not the parent has children. This isn't a relational database, and thinking non-relationally (away from normalization) will yield many performance benefits.
On Tue, May 25, 2010 at 10:50 AM, App Engine N00B < [email protected]> wrote: > Hi! > > I have many models: > > class Parent (db.Model) : > data = db.StringProperty() > > > class Child1 (db.Model) : > parent = db.ReferenceProperty(Parent) > childData = db.StringProperty() > > class Child2 (db.Model) : > parent = db.ReferenceProperty(Parent) > childData2 = db.StringProperty() > > class Child3 (db.Model) : > parent = db.ReferenceProperty(Parent) > childData3 = db.StringProperty() > > .... > > I want a query which can give me a list of all parents which do not > have a child yet. How do i do it? > > I do not want to maintain an identifier in the Parent model for each > of the children as I want to add new child models very often. > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]<google-appengine%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/google-appengine?hl=en. > > -- Ikai Lan Developer Programs Engineer, Google App Engine Blog: http://googleappengine.blogspot.com Twitter: http://twitter.com/app_engine Reddit: http://www.reddit.com/r/appengine -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected]. 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.
