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| <td><h1>Code Igniter User Guide Version 1.5.0</h1></td> | |
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| <h1>Database Caching Class</h1> | |
| <p>The Database Caching Class contains functions that permit you to cache your queries.</p> | |
| <p class="important"><strong>Important:</strong> This class is initialized automatically by the database driver | |
| when caching is enabled. Do NOT load this class manually. | |
| More info below...</p> | |
| <h2>How Does Caching Work?</h2> | |
| <p>When caching is enabled, anytime a "read" type query (SELECT) is run, the result object will | |
| be serialized and stored in a text file on your server. Subsequent calls to that query will use the result from the cache file | |
| rather then accessing your database. In other words, the first time a page is loaded a cache file will be written. | |
| The next time the page is loaded the cached file will be used.</p> | |
| <p>When a "write" type query (INSERT, UPDATE, etc.) is run , any cache files associated with the particular page being viewed | |
| will be deleted automatically. In some cases you may need to update some data with every page load (user stats, for example). | |
| In these cases you'll proabably want to manually disable caching just before running your "write" query, then re-enable it just | |
| after. Otherwise, your site will be caught ina cycle of writing/deleting caches, creating more load then if you were not using | |
| caching. More information on this will be found below.</p> | |
| <p>Although caching will reduce your database load, dealing with cache files does generate more | |
| up-front processing and file-system operations, as cache files are created and read. Instead of accessing your database for information | |
| text files are used.</p> | |
| <p>Whether you see a performance gain as a result of caching is dependant on many factors. | |
| For example, if you have a highly optimized database under very little load, you probably won't see a performance boost. | |
| If your database is under heavy use you probably will see an improved response, assuming your filesystem is not | |
| overly taxed. In some clustered server environments caching may be detrimental since filesystem operations are so intense. | |
| On single servers (particularly in shared enironments) caching will probably be beneficial. Unfortunately there is no | |
| single answer to the question of whether you should cache your database. It really depends on your situation.</p> | |
| <h2>Enabling Caching</h2> | |
| <p>Enabling caching requires three steps:</p> | |
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| <li>Creating a directory on your server where the cache files will be written.</li> | |
| <li>Setting the path to your cache folder in your <dfn>application/config/database.php</dfn> file.</li> | |
| <li>Enalbling the caching preference either in your database config file or manually in your controllers.</li> | |
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