According to the Google docs ( https://developers.google.com/appengine/docs/python/datastore/queries#Query_Projection), projection queries have the following limitations:
- You can only project indexed properties. This means that projecting Text, Blob or other properties explicitly marked as unindexed is not supported. - You cannot project a property that also is referenced in an equality filter. For example SELECT A FROM kind WHERE A = 1 is not supported, but SELECT A FROM kind WHERE B = 1 or SELECT A FROM kind WHERE A > 1 is supported. - You cannot project the same property more than once. - The entities returned by a projection query are only partially populated, so they cannot be saved back to the Datastore. Does the new code avoid doing a projection when text or blob fields are included and when one of the requested fields is referenced in an equality filter? Also, should there be a way to override the projection query (right now it looks like it's automatic whenever you request fewer than all the fields)? Also, are GAE tables allowed to have id fields with names other than "id"? If so, should line 4094 ( http://code.google.com/p/web2py/source/browse/gluon/dal.py#4094): query_projection = [p for p in projection if p != 'id'] if projection \ be changed to something like: query_projection = [p for p in projection if p != self.db[tablename]._id. name] if projection \ Anthony On Sunday, June 10, 2012 10:21:18 PM UTC-4, Massimo Di Pierro wrote: > > Hello Google App Engine users, > > Thanks to howesc we have a new feature in trunk: support for datastore > projections. > The problem and its solution are best explained in this post: > > http://stackoverflow.com/questions/10940995/does-google-app-engine-projection-queries-are-supported-by-web2py > > Pleas help us test it. In particular help us test trunk and make sure it > does not break your GAE apps. > > Massimo >
