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POCaching queries in Django
 

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  1. POCaching queries in Django
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    <p>In a django project I only need to cache a few queries, using, because of server limitations, a cache table instead of memcached.</p> <p>One of those queries looks like this:</p> <p>Let's say I have a <code>Parent</code> object, which has a lot of <code>Child</code> objects. I need to store the result of the simple query <code>parent.childs.all()</code>.</p> <p>I have no problem with that, and everything works as expected with some code like</p> <pre><code>key = "%s_children" %(parent.name) value = cache.get(key) if value is None: cache.set(key, parent.children.all(), CACHE_TIMEOUT) value = cache.get(key) </code></pre> <p>But sometimes, just sometimes, the <code>cache.set</code> does nothing, and, after executing <code>cache.set</code>, <code>cache.get(key)</code> keeps returning <code>None</code>.</p> <p>After some test, I've noticed that <code>cache.set</code> is not working when <code>parent.children.all().count()</code> has higher values.<br /> That means that if I'm storing inside of <code>key</code> (for example) 600 children objects, it works fine, <br /> but it wont work with 1200 children.</p> <p>So <strong>my question is</strong>: <em>is there a limit to the data that a key could store? How can I override it?</em></p> <p><br /> <hr /> <br /> <strong>Second question:</strong> which way is "better", the above code, or the following one?</p> <pre><code>key = "%s_children" %(parent.name) value = cache.get(key) if value is None: value = parent.children.all() cache.set(key, value, CACHE_TIMEOUT) </code></pre> <p>The second version won't cause errors if <code>cache.set</code> doesn't work, so it could be a workaround to my issue, but <em>obviously</em> not a solution.</p> <p>In general, let's forget about my issue, which version would you consider "better"?</p>
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    1. CORegarding updated code: The second version is better. Every call to set or get involves pickling and base64 encoding your data, so minimizing those calls will give better performance.
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      1. USSeth
 

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