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120 lines
11 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>Installs a callback which decides whether a statement is cached</title>
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</head>
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<body class="docs"><div id="layout">
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<div id="layout-content"><div id="function.mysqlnd-qc-set-is-select" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">mysqlnd_qc_set_is_select</h1>
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<p class="verinfo">(PECL mysqlnd_qc >= 1.0.0)</p><p class="refpurpose"><span class="refname">mysqlnd_qc_set_is_select</span> — <span class="dc-title">Installs a callback which decides whether a statement is cached</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.mysqlnd-qc-set-is-select-description">
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<h3 class="title">说明</h3>
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<div class="methodsynopsis dc-description">
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<span class="methodname"><strong>mysqlnd_qc_set_is_select</strong></span>
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( <span class="methodparam">
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<span class="type">string</span>
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<code class="parameter">$callback</code>
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</span>
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) : <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span></div>
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<p class="para rdfs-comment">
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Installs a callback which decides whether a statement is cached.
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</p>
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<p class="para">
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There are several ways of hinting PELC/mysqlnd_qc to cache a query.
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By default, PECL/mysqlnd_qc attempts to cache a if caching of all statements
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is enabled or the query string begins with a certain SQL hint.
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The plugin internally calls a function named <em>is_select()</em>
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to find out. This internal function can be replaced with a user-defined callback.
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Then, the user-defined callback is responsible to decide whether the plugin
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attempts to cache a statement. Because the internal function is replaced
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with the callback, the callback gains full control. The callback is free
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to ignore the configuration setting <em>mysqlnd_qc.cache_by_default</em>
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and SQL hints.
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</p>
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<p class="para">
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The callback is invoked for every statement inspected by the plugin.
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It is given the statements string as a parameter. The callback returns
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<strong><code>FALSE</code></strong> if the statement shall not be cached. It returns <strong><code>TRUE</code></strong> to
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make the plugin attempt to cache the statements result set, if any.
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A so-created cache entry is given the default TTL set with the
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PHP configuration directive <em>mysqlnd_qc.ttl</em>.
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If a different TTL shall be used, the callback returns a numeric
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value to be used as the TTL.
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</p>
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<p class="para">
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The internal <em>is_select</em> function is part of the internal
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cache storage handler interface. Thus, a user-defined storage handler
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offers the same capabilities.
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.mysqlnd-qc-set-is-select-parameters">
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<h3 class="title">参数</h3>
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<p class="para">此函数没有参数。</p>
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</div>
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<div class="refsect1 returnvalues" id="refsect1-function.mysqlnd-qc-set-is-select-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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成功时返回 <strong><code>TRUE</code></strong>， 或者在失败时返回 <strong><code>FALSE</code></strong>。
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.mysqlnd-qc-set-is-select-examples">
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<h3 class="title">范例</h3>
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<div class="example" id="example-2300">
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<p><strong>Example #1 <span class="function"><strong>mysqlnd_qc_set_is_select()</strong></span> example</strong></p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">/* callback which decides if query is cached */<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">is_select</span><span style="color: #007700">(</span><span style="color: #0000BB">$query</span><span style="color: #007700">) {<br /> static </span><span style="color: #0000BB">$patterns </span><span style="color: #007700">= array(<br /> </span><span style="color: #FF8000">/* true - use default from mysqlnd_qc.ttl */<br /> </span><span style="color: #DD0000">"@SELECT\s+.*\s+FROM\s+test@ismU" </span><span style="color: #007700">=> </span><span style="color: #0000BB">true</span><span style="color: #007700">,<br /> </span><span style="color: #FF8000">/* 3 - use TTL = 3 seconds */<br /> </span><span style="color: #DD0000">"@SELECT\s+.*\s+FROM\s+news@ismU" </span><span style="color: #007700">=> </span><span style="color: #0000BB">3<br /> </span><span style="color: #007700">);<br /> </span><span style="color: #FF8000">/* check if query does match pattern */<br /> </span><span style="color: #007700">foreach (</span><span style="color: #0000BB">$patterns </span><span style="color: #007700">as </span><span style="color: #0000BB">$pattern </span><span style="color: #007700">=> </span><span style="color: #0000BB">$ttl</span><span style="color: #007700">) {<br /> if (</span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #0000BB">$pattern</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">)) {<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"is_select(%45s): cache\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /> return </span><span style="color: #0000BB">$ttl</span><span style="color: #007700">;<br /> }<br /> }<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"is_select(%45s): do not cache\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /> return </span><span style="color: #0000BB">false</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">mysqlnd_qc_set_is_select</span><span style="color: #007700">(</span><span style="color: #DD0000">"is_select"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* Connect, create and populate test table */<br /></span><span style="color: #0000BB">$mysqli </span><span style="color: #007700">= new </span><span style="color: #0000BB">mysqli</span><span style="color: #007700">(</span><span style="color: #DD0000">"host"</span><span style="color: #007700">, </span><span style="color: #DD0000">"user"</span><span style="color: #007700">, </span><span style="color: #DD0000">"password"</span><span style="color: #007700">, </span><span style="color: #DD0000">"schema"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"DROP TABLE IF EXISTS test"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"CREATE TABLE test(id INT)"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"INSERT INTO test(id) VALUES (1), (2), (3)"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* cache put */<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT id FROM test WHERE id = 1"</span><span style="color: #007700">);<br /></span><span style="color: #FF8000">/* cache hit */<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT id FROM test WHERE id = 1"</span><span style="color: #007700">);<br /></span><span style="color: #FF8000">/* cache put */<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT * FROM test"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
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</span>
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</pre></div>
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</div>
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<div class="example-contents"><p>以上例程会输出：</p></div>
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<div class="example-contents screen">
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<div class="cdata"><pre>
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is_select( DROP TABLE IF EXISTS test): do not cache
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is_select( CREATE TABLE test(id INT)): do not cache
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is_select( INSERT INTO test(id) VALUES (1), (2), (3)): do not cache
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is_select( SELECT id FROM test WHERE id = 1): cache
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is_select( SELECT id FROM test WHERE id = 1): cache
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is_select( SELECT * FROM test): cache
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</pre></div>
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</div>
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</div>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.mysqlnd-qc-set-is-select-seealso">
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<h3 class="title">参见</h3>
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<p class="para">
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<ul class="simplelist">
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<li class="member">
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<a href="mysqlnd_qc.configuration.html" class="link">Runtime configuration</a>
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</li>
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<li class="member">
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<a href="mysqlnd-qc.configuration.html#ini.mysqlnd-qc.ttl" class="link">mysqlnd_qc.ttl</a>
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</li>
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<li class="member">
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<a href="mysqlnd-qc.configuration.html#ini.mysqlnd-qc.cache-by-default" class="link">mysqlnd_qc.cache_by_default</a>
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</li>
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<li class="member">
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<span class="function"><a href="mysqlnd_qc_set_user_handlers.html" class="function" rel="rdfs-seeAlso">mysqlnd_qc_set_user_handlers()</a> - Sets the callback functions for a user-defined procedural storage handler</span>
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</li>
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</ul>
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</p>
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</div>
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</div></div></div></body></html> |