How to sum only positive values, with Django conditional aggregates?
<p>I have a table that looks like this:</p>

<pre><code>class MeasureValue(models.Model):
    cost_saving_10th = models.FloatField(null=True, blank=True)
</code></pre>

<p>I know how to get the sum of all the values:</p>

<pre><code>mvs.aggregate(Sum('cost_saving')).values()[0]
</code></pre>

<p>But how do I get the sum of all the <em>positive</em> values? I think I need a conditional aggregate, but I'm not sure how to do this. </p>