GAE does not have a notion of Tables like an SQL Database, there are NO rows in GAE. In SQL when you add a *column* to a table, for all the existing *rows* the value is set to NULL. In GAE when you add a *property*, all the existing *objects* have an empty value for this property, they are NOT updated because the model definition is changed. The empty value is determined when you fetch such an *object*. In the decoded protobuffer you find that the object has no value for the new property. These objects are not in the index table for this new property because the index is only updated on a put() operation.
2010/2/25 Ikai L (Google) <[email protected]>: > I believe so. What have you observed when saving your models? > > On Wed, Feb 24, 2010 at 12:55 PM, Jairo Vasquez <[email protected]> > wrote: >> >> Thanks Ikai, >> >> But what is the difference between empty values and None when you >> define a Model in GAE? Because you just define a property without a >> default value and when you create an instance of that entity, the >> value will be None isn't it? >> >> On Feb 24, 1:36 pm, "Ikai L (Google)" <[email protected]> wrote: >> > That *should* create an index. We index null values, but we don't index >> > empty values. That is, if you have an entity: >> > >> > Animal { >> > String name; >> > int age; >> > >> > } >> > >> > And create 100 entities, then add: >> > >> > Animal { >> > String name; >> > int age; >> > String nickname; >> > >> > } >> > >> > The 100 entities that were created will have an EMPTY nickname and will >> > not >> > be queryable by this attribute, but Animals created after the change >> > that >> > populate this field will be indexable. >> > >> > On Tue, Feb 23, 2010 at 9:58 PM, Jairo Vasquez Moreno < >> > >> > >> > >> > >> > >> > [email protected]> wrote: >> > > Hi Nick, >> > >> > > I know every write to Datastore creates an index entry for each >> > > indexable >> > > value. But when a value is not set (None) will an index entry be >> > > created? >> > >> > > My doubt is, is it better to let a property None and then filter by >> > > property=None or set the with something e.g property="-1" and then >> > > filter by >> > > property="-1". Because I'm leaving a property as None and then doing >> > > some >> > > stuff with those entity with None but this is generating more >> > > DeadLineExcedeed errors as expected (even decreasing the number of >> > > entities >> > > to fetch) so I think maybe the filter is getting to much time and I >> > > don't >> > > know what else could be. >> > >> > > Thanks in advance. >> > >> > > -- >> > > Jairo Vasquez Moreno >> > > Mentez Developer >> > >www.mentez.com >> > > Medellin - Colombia >> > >> > > -- >> > > 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%2Bunsubscrib >> > > [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 >> > Enginehttp://googleappengine.blogspot.com|http://twitter.com/app_engine >> >> -- >> 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. >> > > > > -- > Ikai Lan > Developer Programs Engineer, Google App Engine > http://googleappengine.blogspot.com | http://twitter.com/app_engine > > -- > 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. > -- 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.
