James Bennett wrote:
> While we're on the topic, the docs explicitly advise against doing
> 'len' on a QuerySet because of the potential memory overhead of
> loading all the objects, and recommend using the QuerySet's 'count'
> method instead. Would it make more sense, then, to internally change
> '__len__' on QuerySet to just return the result of 'self.count()' and
> remove this potential hazard altogether?
The distinction was made on purpose. Tag {% for %} evaluates length of
an iterable by doing len() and if this would call .count() then in most
common case all queries accessed from templates will execute two
request: "select count" and then "select" to actually output things. Now
it only makes one select when doing len() and then uses newly cached
results for output.
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