41 lines
2.1 KiB
PHP
41 lines
2.1 KiB
PHP
Doctrine has very comprehensive and fast caching solution.
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Its cache is <b>always up-to-date</b>.
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In order to achieve this doctrine does the following things:
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<br /><br />
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<table border=1 class='dashed' cellpadding=0 cellspacing=0>
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<tr><td>
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1. Every Doctrine_Table has its own cache directory. The default is cache/componentname/. All the cache files are saved into that directory.
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The format of each cache file is [primarykey].cache.
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<br /><br />
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2. When retrieving records from the database doctrine always tries to hit the cache first.
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3. If a record (Doctrine_Record) is retrieved from database or inserted into database it will be saved into cache.
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<br /><br />
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4. When a Data Access Object is deleted or updated it will be deleted from the cache
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</td></tr>
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</table>
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<br /><br />
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Now one might wonder that this kind of solution won't work since eventually the cache will be a copy of database!
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So doctrine does the following things to ensure the cache won't get too big:
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<br /><br />
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<table border=1 class='dashed' cellpadding=0 cellspacing=0>
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<tr><td>
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1. Every time a cache file is accessed the id of that record will be added into the $fetched property of Doctrine_Cache
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2. At the end of each script the Doctrine_Cache destructor will write all these primary keys at the end of a stats.cache file
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<br /><br />
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3. Doctrine does propabalistic cache cleaning. The default interval is 200 page loads (= 200 constructed Doctrine_Managers). Basically this means
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that the average number of page loads between cache cleans is 200.
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<br /><br />
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4. On every cache clean stats.cache files are being read and the least accessed cache files
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(cache files that have the smallest id occurance in the stats file) are then deleted.
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For example if the cache size is set to 200 and the number of files in cache is 300, then 100 least accessed files are being deleted.
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Doctrine also clears every stats.cache file.
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</td></tr>
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</table>
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<br /><br />
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So for every 199 fast page loads there is one page load which suffers a little overhead from the cache cleaning operation.
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