#28601: do not cache default callable return value of None in get_or_set
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Reporter: Dan Tao | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Core (Cache system) | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Description changed by Dan Tao:
Old description:
> In [82be474
> https://github.com/django/django/commit/82be474efa81e5f2e127d711045a2ec06b206a8e]
> the change was made to allow None as a default value passed to
> BaseCache.get_or_set. In case the default value of None is used, it is
> not
> stored in the cache. This still left open the possibility that default
> could
> be a callable that returns None, in which case it would be stored in the
> cache.
>
> {{{
> # This scenario works as expected.
> cache.get_or_set('foo', None) # None
> cache.get_or_set('foo', 5) # 5
> cache.get('foo') # 5
>
> # This scenario seems wrong.
> cache.get_or_set('bar', lambda: None) # None
> cache.get_or_set('bar', 5) # None :(
> cache.get('bar') # None :(
> }}}
New description:
In
[https://github.com/django/django/commit/82be474efa81e5f2e127d711045a2ec06b206a8e
82be474] the change was made to allow None as a default value passed to
BaseCache.get_or_set. In case the default value of None is used, it is not
stored in the cache. This still left open the possibility that default
could
be a callable that returns None, in which case it would be stored in the
cache.
{{{
# This scenario works as expected.
cache.get_or_set('foo', None) # None
cache.get_or_set('foo', 5) # 5
cache.get('foo') # 5
# This scenario seems wrong.
cache.get_or_set('bar', lambda: None) # None
cache.get_or_set('bar', 5) # None :(
cache.get('bar') # None :(
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/28601#comment:4>
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