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POHow reliable is NDB's put()?
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copied!<p>I'm having some strange behavior with my models.</p> <p>I have Event model, which keeps tracks of events. And an "Aggregate" model, which stores an aggregate of records of model A, grouped by date.</p> <pre><code>class Event(ndb.Model): user = ndb.KeyProperty(kind=UserProfile) date = ndb.DateTimeProperty(auto_now_add=True) event_type = ndb.StringProperty() is_aggregated = ndb.BooleanProperty(default=False) class Aggregate(ndb.Model): user = ndb.KeyProperty(kind=UserProfile) date = ndb.DateProperty() aggregates = ndb.PickleProperty(default={}) </code></pre> <p><strong><code>Event</code></strong> has an <code>aggregate()</code> method, like so:</p> <pre><code>def aggregate(self): if self.is_aggregated: # already aggregated return # get an existing aggregate agg = Aggregate.query( Aggregate.user == self.user, Aggregate.date == self.date.date() ).get() if not agg: # or create a new one agg = Aggregate( user=self.user, date=self.date.date() ) agg.put() # update aggregate's count if self.event_type not in agg.aggregates.keys(): agg.aggregates[self.event_type] = 0 agg.aggregates[self.event_type] += 1 agg.put() # mark this as aggregated self.is_aggregated = True self.put() </code></pre> <p>Now, in my handlers, every time a new <code>Event</code> is created, I call its <code>aggregate</code> method. But there's some discrepancy with the numbers. </p> <p>For example, I have 20 <code>Event</code> records with the <code>date</code> between <code>2013-10-10 00:00:00</code> and <code>2013-10-10 23:59:59</code> and <code>event_type = "add"</code>, all of them have <code>is_aggregated = True</code>. That would imply that the <code>aggregate</code> method executed successfully for each.</p> <p>But when I view the corresponding <code>Aggregate</code> record with the <code>date = 2013-10-10</code>, the <code>aggregates</code> property doesn't reflect 20 <code>"add"</code> events. It only has 16.</p> <p>What would cause such a discrepancy? How would <code>self.put()</code> succeed but <code>agg.put()</code> not succeed?</p>

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