ReferenceProperty prefetching in App Engine - Nick's Blog

Posted by Nick Johnson | Filed under python, tech, app-engine, cookbook, coding This post is a brief interlude in the webapps on App Engine series. Fear not, it'll be back! Frequently, we need to do a datastore query for a set of records, then do something with a property referenced by each of those records. For example, supposing we are writing a blogging system, and we want to display a list of

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ReferencePropertyを参照する際にKeyをプリフェッチしてドンのほうがこすとすくないぜーだそうです。

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On the surface, this looks fine. If we look closer, however - perhaps by using Guido's excellent AppStats tool, we'll notice that each iteration of the loop, we're performing a get request for the referenced author entity. This happens the first time we dereference any ReferenceProperty, even if we