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Answer 1

A:

You don't use filter() to query for an ancestor. Try instead:

M.all().ancestor(None).fetch(100)

Edit: hmm, that won't work apparently (I'd swear I had done this somewhere). So you'd need to save an extra property as a flag for root entities.

moraes 2010-07-25 21:02:46

I don't want to look for ancestor (which I understand is the parent or the parent's parent or the parent's parent's parent etc). Instead, I want to query for the immediate parent.

Martin v. Löwis 2010-07-25 21:33:03

When your create an entity with parent=None, it is an entity with no ancestor. You don't query for it using .filter('parent', ...), but using .ancestor().To be able to query for immediate parent, you need to store an extra property for the parent and query on that.

moraes 2010-07-26 08:23:41

Answer 2

+1 A:

There's no way to query specifically for root entities. You need to either use external information (eg, no entity of type Foo has parents), or add a property that indicates if an entity is a root entity or not.

Nick Johnson 2010-07-26 12:46:51

That's sad. I wonder what the point then is for having a hierarchy of objects at all.

Martin v. Löwis 2010-07-26 21:44:53

So you can quickly find descendent entities, and look up the parent of an entity, and to provide transactional domains.

Nick Johnson 2010-07-27 08:35:56

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AppEngine query for None parent

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