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I have seen the in GAE datastore there are so many entity which at the end are Strings, at least apparently.

List of GAE Java Datastore Entities

I'd like to know the underneath reason for that? indexing? semantic search?

Jordi P.S.
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  • It's not quite clear what you are asking - are you asking "Why does GAE have special datastore types for things like User and Email and GeoPt and Category and whatnot?" These aren't "entities" (a word which has special meaning) or "entity groups" (another term which has special meaning). – stickfigure Mar 21 '12 at 23:26
  • Entity is what you will have for your domain object. Entity group is how you would group them. And possible types like String etc are Data types which you can use in entity, you can use an Entity too. I suggest you clarify these concepts first, as question is completely misplaced. – Vishal Biyani Mar 22 '12 at 01:01
  • I meant group of entities, not entity groups, sorry. – Jordi P.S. Mar 22 '12 at 09:22

2 Answers2

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It's quite clear to me -- the question is what were we (Google App Engine designers) thinking when we added those "semantic" property types.

I wasn't on the team then, but I think we were enamored with automatically generating XML from entities using the ATOM schema. I don't think this is very popular or useful in practice. You're free to ignore these -- their validation is all trivial (must not be empty).

In NDB (a new Python client for the datastore) I decided not to support these semantic property types or XML generation and so far only one person requested it: http://code.google.com/p/appengine-ndb-experiment/issues/detail?id=96

Guido van Rossum
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  • Thanks for the answer Guido. App engine developers appreciate that people from the design team answer those kind of questions. – Jordi P.S. Mar 29 '12 at 19:47
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I had the same question a couple years ago. Nick answered it here. The Java classes provide parity with Python, and in Python it's useful for the special .to_xml() behaviour. It's possible that when GAE gets proper GEO queries the GeoPt might become useful but otherwise you can ignore them.

Community
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Richard Watson
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