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POyii caching and couchbase
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copied!<p>need some help to clarify the concept.</p> <pre><code>$sql = 'SELECT * FROM tbl_post LIMIT 20'; $dependency = new CDbCacheDependency('SELECT MAX(update_time) FROM tbl_post'); $rows = Yii::app()->db->cache(1000, $dependency)->createCommand($sql)->queryAll(); </code></pre> <p>1.if the cache contains an entry indexed by the SQL statement.</p> <p>2.if the dependency has not changed (the maximum update_time value is the same as when the query result was saved in the cache).</p> <p>I do not understand what do the above explanation means. Especially second one with regards to maximum update_time. Please correct me if I am wrong.</p> <p>There is a update_time column in tbl_post table. Whenever a row is updated, the update_time is updated too. If a post is retrieved from the cache, CDbCacheDependency will first query the database for MAX(update_time)? What is the purpose of this and how exactly does it works in keeping the cache updated?</p> <p>Another question is regarding memcache. I understand that it is possible to cluster memcache servers. Say I have the below configurations.</p> <p>1 memcache server in US. 1 memcache server in Europe.</p> <p>My Yii website makes use of the cluster of 2 nodes. memcache will split the caching between the 2 nodes.</p> <p>1.user A retrieves a post from database and cached it. assume (123,$model) in US node.</p> <p>2.user B wants to retrieve the same post, from Europe. Will looking for key 123 finds the cache? Does it matters if both users are in US or Europe?</p> <p>Thanks!! </p>

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