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diff --git a/user_guide/database/caching.html b/user_guide/database/caching.html new file mode 100644 index 000000000..883a7a81e --- /dev/null +++ b/user_guide/database/caching.html @@ -0,0 +1,643 @@ + + +<!DOCTYPE html> +<!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]--> +<!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]--> +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + + <title>Database Caching Class — CodeIgniter 3.1.5 documentation</title> + + + + + <link rel="shortcut icon" href="../_static/ci-icon.ico"/> + + + + <link href='https://fonts.googleapis.com/css?family=Lato:400,700,400italic,700italic|Roboto+Slab:400,700|Inconsolata:400,700&subset=latin,cyrillic' rel='stylesheet' type='text/css'> + + + + + + + + + + <link rel="stylesheet" href="../_static/css/citheme.css" type="text/css" /> + + + + <link rel="top" title="CodeIgniter 3.1.5 documentation" href="../index.html"/> + <link rel="up" 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+<li class="toctree-l2"><a class="reference internal" href="../general/helpers.html">Helpers</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/libraries.html">Using CodeIgniter Libraries</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/creating_libraries.html">Creating Libraries</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/drivers.html">Using CodeIgniter Drivers</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/creating_drivers.html">Creating Drivers</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/core_classes.html">Creating Core System Classes</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/ancillary_classes.html">Creating Ancillary Classes</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/hooks.html">Hooks - Extending the Framework Core</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/autoloader.html">Auto-loading Resources</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/common_functions.html">Common Functions</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/compatibility_functions.html">Compatibility Functions</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/routing.html">URI Routing</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/errors.html">Error Handling</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/caching.html">Caching</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/profiling.html">Profiling Your Application</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/cli.html">Running via the CLI</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/managing_apps.html">Managing your Applications</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/environments.html">Handling Multiple Environments</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/alternative_php.html">Alternate PHP Syntax for View Files</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/security.html">Security</a></li> +<li class="toctree-l2"><a class="reference internal" href="../general/styleguide.html">PHP Style Guide</a></li> +</ul> +</li> +</ul> +<ul> +<li class="toctree-l1"><a class="reference internal" href="../libraries/index.html">Libraries</a><ul> +<li class="toctree-l2"><a class="reference internal" href="../libraries/benchmark.html">Benchmarking Class</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/caching.html">Caching Driver</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/calendar.html">Calendaring Class</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/cart.html">Shopping Cart Class</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/config.html">Config Class</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/email.html">Email Class</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/encrypt.html">Encrypt Class</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/encryption.html">Encryption Library</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/file_uploading.html">File Uploading Class</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/form_validation.html">Form Validation</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/ftp.html">FTP Class</a></li> +<li class="toctree-l2"><a 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XML-RPC Server Classes</a></li> +<li class="toctree-l2"><a class="reference internal" href="../libraries/zip.html">Zip Encoding Class</a></li> +</ul> +</li> +</ul> +<ul class="current"> +<li class="toctree-l1 current"><a class="reference internal" href="index.html">Database Reference</a><ul class="current"> +<li class="toctree-l2"><a class="reference internal" href="examples.html">Quick Start: Usage Examples</a></li> +<li class="toctree-l2"><a class="reference internal" href="configuration.html">Database Configuration</a></li> +<li class="toctree-l2"><a class="reference internal" href="connecting.html">Connecting to a Database</a></li> +<li class="toctree-l2"><a class="reference internal" href="queries.html">Running Queries</a></li> +<li class="toctree-l2"><a class="reference internal" href="results.html">Generating Query Results</a></li> +<li class="toctree-l2"><a class="reference internal" href="helpers.html">Query Helper Functions</a></li> +<li class="toctree-l2"><a class="reference internal" href="query_builder.html">Query Builder Class</a></li> +<li class="toctree-l2"><a class="reference internal" href="transactions.html">Transactions</a></li> +<li class="toctree-l2"><a class="reference internal" href="metadata.html">Getting MetaData</a></li> +<li class="toctree-l2"><a class="reference internal" href="call_function.html">Custom Function Calls</a></li> +<li class="toctree-l2 current"><a class="current reference internal" href="">Query Caching</a></li> +<li class="toctree-l2"><a class="reference internal" href="forge.html">Database Manipulation with Database Forge</a></li> +<li class="toctree-l2"><a class="reference internal" href="utilities.html">Database Utilities Class</a></li> +<li class="toctree-l2"><a class="reference internal" href="db_driver_reference.html">Database Driver Reference</a></li> +</ul> +</li> +</ul> +<ul> +<li class="toctree-l1"><a class="reference internal" href="../helpers/index.html">Helpers</a><ul> +<li class="toctree-l2"><a 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href="../helpers/text_helper.html">Text Helper</a></li> +<li class="toctree-l2"><a class="reference internal" href="../helpers/typography_helper.html">Typography Helper</a></li> +<li class="toctree-l2"><a class="reference internal" href="../helpers/url_helper.html">URL Helper</a></li> +<li class="toctree-l2"><a class="reference internal" href="../helpers/xml_helper.html">XML Helper</a></li> +</ul> +</li> +</ul> + + + + </div> + + </nav> + + <section data-toggle="wy-nav-shift" class="wy-nav-content-wrap"> + + + <nav class="wy-nav-top" role="navigation" aria-label="top navigation"> + <i data-toggle="wy-nav-top" class="fa fa-bars"></i> + <a href="../index.html">CodeIgniter</a> + </nav> + + + + <div class="wy-nav-content"> + <div class="rst-content"> + <div role="navigation" aria-label="breadcrumbs navigation"> + <ul class="wy-breadcrumbs"> + <li><a href="../index.html">Docs</a> »</li> + + <li><a href="index.html">Database Reference</a> »</li> + + <li>Database Caching Class</li> + <li class="wy-breadcrumbs-aside"> + + </li> + <div style="float:right;margin-left:5px;" id="closeMe"> + <img title="Classic Layout" alt="classic layout" src="data:image/gif;base64,R0lGODlhFAAUAJEAAAAAADMzM////wAAACH5BAUUAAIALAAAAAAUABQAAAImlI+py+0PU5gRBRDM3DxbWoXis42X13USOLauUIqnlsaH/eY6UwAAOw==" /> + </div> + </ul> + <hr/> +</div> + <div role="main" class="document"> + + <div class="section" id="database-caching-class"> +<h1>Database Caching Class<a class="headerlink" href="#database-caching-class" title="Permalink to this headline">¶</a></h1> +<p>The Database Caching Class permits you to cache your queries as text +files for reduced database load.</p> +<div class="admonition important"> +<p class="first admonition-title">Important</p> +<p class="last">This class is initialized automatically by the database +driver when caching is enabled. Do NOT load this class manually.</p> +</div> +<div class="admonition important"> +<p class="first admonition-title">Important</p> +<p class="last">Not all query result functions are available when you +use caching. Please read this page carefully.</p> +</div> +<div class="section" id="enabling-caching"> +<h2>Enabling Caching<a class="headerlink" href="#enabling-caching" title="Permalink to this headline">¶</a></h2> +<p>Caching is enabled in three steps:</p> +<ul class="simple"> +<li>Create a writable directory on your server where the cache files can +be stored.</li> +<li>Set the path to your cache folder in your +application/config/database.php file.</li> +<li>Enable the caching feature, either globally by setting the preference +in your application/config/database.php file, or manually as +described below.</li> +</ul> +<p>Once enabled, caching will happen automatically whenever a page is +loaded that contains database queries.</p> +</div> +<div class="section" id="how-does-caching-work"> +<h2>How Does Caching Work?<a class="headerlink" href="#how-does-caching-work" title="Permalink to this headline">¶</a></h2> +<p>CodeIgniter’s query caching system happens dynamically when your pages +are viewed. When caching is enabled, the first time a web page is +loaded, the query result object will be serialized and stored in a text +file on your server. The next time the page is loaded the cache file +will be used instead of accessing your database. Your database usage can +effectively be reduced to zero for any pages that have been cached.</p> +<p>Only read-type (SELECT) queries can be cached, since these are the only +type of queries that produce a result. Write-type (INSERT, UPDATE, etc.) +queries, since they don’t generate a result, will not be cached by the +system.</p> +<p>Cache files DO NOT expire. Any queries that have been cached will remain +cached until you delete them. The caching system permits you clear +caches associated with individual pages, or you can delete the entire +collection of cache files. Typically you’ll want to use the housekeeping +functions described below to delete cache files after certain events +take place, like when you’ve added new information to your database.</p> +</div> +<div class="section" id="will-caching-improve-your-site-s-performance"> +<h2>Will Caching Improve Your Site’s Performance?<a class="headerlink" href="#will-caching-improve-your-site-s-performance" title="Permalink to this headline">¶</a></h2> +<p>Getting a performance gain as a result of caching depends on many +factors. 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 +file-system is not overly taxed. Remember that caching simply changes +how your information is retrieved, shifting it from being a database +operation to a file-system one.</p> +<p>In some clustered server environments, for example, caching may be +detrimental since file-system operations are so intense. On single +servers in shared environments, 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> +</div> +<div class="section" id="how-are-cache-files-stored"> +<h2>How are Cache Files Stored?<a class="headerlink" href="#how-are-cache-files-stored" title="Permalink to this headline">¶</a></h2> +<p>CodeIgniter places the result of EACH query into its own cache file. +Sets of cache files are further organized into sub-folders corresponding +to your controller functions. To be precise, the sub-folders are named +identically to the first two segments of your URI (the controller class +name and function name).</p> +<p>For example, let’s say you have a controller called blog with a function +called comments that contains three queries. The caching system will +create a cache folder called blog+comments, into which it will write +three cache files.</p> +<p>If you use dynamic queries that change based on information in your URI +(when using pagination, for example), each instance of the query will +produce its own cache file. It’s possible, therefore, to end up with +many times more cache files than you have queries.</p> +</div> +<div class="section" id="managing-your-cache-files"> +<h2>Managing your Cache Files<a class="headerlink" href="#managing-your-cache-files" title="Permalink to this headline">¶</a></h2> +<p>Since cache files do not expire, you’ll need to build deletion routines +into your application. For example, let’s say you have a blog that +allows user commenting. Whenever a new comment is submitted you’ll want +to delete the cache files associated with the controller function that +serves up your comments. You’ll find two delete functions described +below that help you clear data.</p> +</div> +<div class="section" id="not-all-database-functions-work-with-caching"> +<h2>Not All Database Functions Work with Caching<a class="headerlink" href="#not-all-database-functions-work-with-caching" title="Permalink to this headline">¶</a></h2> +<p>Lastly, we need to point out that the result object that is cached is a +simplified version of the full result object. For that reason, some of +the query result functions are not available for use.</p> +<p>The following functions ARE NOT available when using a cached result +object:</p> +<ul class="simple"> +<li>num_fields()</li> +<li>field_names()</li> +<li>field_data()</li> +<li>free_result()</li> +</ul> +<p>Also, the two database resources (result_id and conn_id) are not +available when caching, since result resources only pertain to run-time +operations.</p> +<div class="section" id="function-reference"> +<h3>Function Reference<a class="headerlink" href="#function-reference" title="Permalink to this headline">¶</a></h3> +</div> +</div> +<div class="section" id="this-db-cache-on-this-db-cache-off"> +<h2>$this->db->cache_on() / $this->db->cache_off()<a class="headerlink" href="#this-db-cache-on-this-db-cache-off" title="Permalink to this headline">¶</a></h2> +<p>Manually enables/disables caching. This can be useful if you want to +keep certain queries from being cached. Example:</p> +<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Turn caching on</span> +<span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">cache_on</span><span class="p">();</span> +<span class="nv">$query</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">query</span><span class="p">(</span><span class="s2">"SELECT * FROM mytable"</span><span class="p">);</span> + +<span class="c1">// Turn caching off for this one query</span> +<span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">cache_off</span><span class="p">();</span> +<span class="nv">$query</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">query</span><span class="p">(</span><span class="s2">"SELECT * FROM members WHERE member_id = '</span><span class="si">$current_user</span><span class="s2">'"</span><span class="p">);</span> + +<span class="c1">// Turn caching back on</span> +<span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">cache_on</span><span class="p">();</span> +<span class="nv">$query</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">query</span><span class="p">(</span><span class="s2">"SELECT * FROM another_table"</span><span class="p">);</span> +</pre></div> +</div> +</div> +<div class="section" id="this-db-cache-delete"> +<h2>$this->db->cache_delete()<a class="headerlink" href="#this-db-cache-delete" title="Permalink to this headline">¶</a></h2> +<p>Deletes the cache files associated with a particular page. This is +useful if you need to clear caching after you update your database.</p> +<p>The caching system saves your cache files to folders that correspond to +the URI of the page you are viewing. For example, if you are viewing a +page at example.com/index.php/blog/comments, the caching system will put +all cache files associated with it in a folder called blog+comments. To +delete those particular cache files you will use:</p> +<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">cache_delete</span><span class="p">(</span><span class="s1">'blog'</span><span class="p">,</span> <span class="s1">'comments'</span><span class="p">);</span> +</pre></div> +</div> +<p>If you do not use any parameters the current URI will be used when +determining what should be cleared.</p> +</div> +<div class="section" id="this-db-cache-delete-all"> +<h2>$this->db->cache_delete_all()<a class="headerlink" href="#this-db-cache-delete-all" title="Permalink to this headline">¶</a></h2> +<p>Clears all existing cache files. Example:</p> +<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">cache_delete_all</span><span class="p">();</span> +</pre></div> +</div> +</div> +</div> + + + </div> + <footer> + + <div class="rst-footer-buttons" role="navigation" aria-label="footer navigation"> + + <a href="forge.html" class="btn btn-neutral float-right" title="Database Forge Class">Next <span class="fa fa-arrow-circle-right"></span></a> + + + <a href="call_function.html" class="btn btn-neutral" title="Custom Function Calls"><span class="fa fa-arrow-circle-left"></span> Previous</a> + + </div> + + + <hr/> + + <div role="contentinfo"> + <p> + © Copyright 2014 - 2017, British Columbia Institute of Technology. + Last updated on Jun 19, 2017. + </p> + </div> + + Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>. + +</footer> + </div> + </div> + + </section> + + </div> + + + + + + <script type="text/javascript"> + var DOCUMENTATION_OPTIONS = { + URL_ROOT:'../', + VERSION:'3.1.5', + COLLAPSE_INDEX:false, + FILE_SUFFIX:'.html', + HAS_SOURCE: false + }; + </script> + <script type="text/javascript" src="../_static/jquery.js"></script> + <script type="text/javascript" src="../_static/underscore.js"></script> + <script type="text/javascript" src="../_static/doctools.js"></script> + + + + + + <script type="text/javascript" src="../_static/js/theme.js"></script> + + + + + <script type="text/javascript"> + jQuery(function () { + SphinxRtdTheme.StickyNav.enable(); + }); + </script> + + +</body> +</html>
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