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178 lines
18 KiB
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<!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>Sets a callback for user-defined read/write splitting</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-ms-set-user-pick-server" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">mysqlnd_ms_set_user_pick_server</h1>
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<p class="verinfo">(PECL mysqlnd_ms < 1.1.0)</p><p class="refpurpose"><span class="refname">mysqlnd_ms_set_user_pick_server</span> — <span class="dc-title">Sets a callback for user-defined read/write splitting</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.mysqlnd-ms-set-user-pick-server-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_ms_set_user_pick_server</strong></span>
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( <span class="methodparam"><span class="type">string</span> <code class="parameter">$function</code></span>
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) : <span class="type">bool</span></div>
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<p class="para rdfs-comment">
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Sets a callback for user-defined read/write splitting. The plugin will
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call the callback only if <em>pick[]=user</em> is the default
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rule for server picking in the relevant section of the plugins configuration
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file.
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</p>
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<p class="para">
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The plugins built-in read/write query split mechanism decisions can be
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overwritten in two ways. The easiest way is to prepend the query string
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with the SQL hints <strong><code>MYSQLND_MS_MASTER_SWITCH</code></strong>,
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<strong><code>MYSQLND_MS_SLAVE_SWITCH</code></strong> or
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<strong><code>MYSQLND_MS_LAST_USED_SWITCH</code></strong>. Using SQL hints one can
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control, for example, whether a query shall be send to the MySQL replication
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master server or one of the slave servers. By help of SQL hints it is
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not possible to pick a certain slave server for query execution.
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</p>
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<p class="para">
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Full control on server selection can be gained using a callback function.
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Use of a callback is recommended to expert users only because the callback
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has to cover all cases otherwise handled by the plugin.
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</p>
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<p class="para">
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The plugin will invoke the callback function for selecting a server from the
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lists of configured master and slave servers. The callback function
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inspects the query to run and picks a server for query execution by returning
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the hosts URI, as found in the master and slave list.
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</p>
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<p class="para">
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If the lazy connections are enabled and the callback chooses a slave server for
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which no connection has been established so far and establishing the connection
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to the slave fails, the plugin will return an error upon the next action
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on the failed connection, for example, when running a query. It is the
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responsibility of the application developer to handle the error. For example,
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the application can re-run the query to trigger a new server selection and
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callback invocation. If so, the callback must make sure to select
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a different slave, or check slave availability, before returning to
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the plugin to prevent an endless loop.
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.mysqlnd-ms-set-user-pick-server-parameters">
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<h3 class="title">参数</h3>
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<dl>
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<dt>
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<code class="parameter">function</code></dt>
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<dd>
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<p class="para">
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The function to be called. Class methods may also be invoked
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statically using this function by passing
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<em>array($classname, $methodname)</em> to this parameter.
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Additionally class methods of an object instance may be called by passing
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<em>array($objectinstance, $methodname)</em> to this parameter.
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</p>
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</dd>
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</dl>
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</div>
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<div class="refsect1 returnvalues" id="refsect1-function.mysqlnd-ms-set-user-pick-server-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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Host to run the query on. The host URI is to be taken from the
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master and slave connection lists passed to the callback function.
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If callback returns a value neither found in the master nor in the slave
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connection lists the plugin will fallback to the second pick method configured
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via the <em>pick[]</em> setting in the plugin configuration file.
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If not second pick method is given, the plugin falls back to the build-in
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default pick method for server selection.
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</p>
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</div>
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<div class="refsect1 unknown-returnvaluet" id="refsect1-function.mysqlnd-ms-set-user-pick-server-unknown-returnvaluet">
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<h3 class="title">注释</h3>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<p class="para">
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<span class="function"><strong>mysqlnd_ms_set_user_pick_server()</strong></span> is available
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with PECL mysqlnd_ms < 1.1.0. It has been replaced by the
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<em>user</em> filter. Please, check the
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<a href="mysqlnd_ms.changes_one_one.html" class="link">Change History</a>
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for upgrade notes.
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</p>
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</p></blockquote>
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</div>
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<div class="refsect1 examples" id="refsect1-function.mysqlnd-ms-set-user-pick-server-examples">
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<h3 class="title">范例</h3>
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<p class="para">
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<div class="example" id="example-2276">
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<p><strong>Example #1 <span class="function"><strong>mysqlnd_ms_set_user_pick_server()</strong></span> example</strong></p>
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<div class="example-contents">
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<div class="inicode"><pre class="inicode">[myapp]
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master[] = localhost
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slave[] = 192.168.2.27:3306
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slave[] = 192.168.78.136:3306
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pick[] = user</pre>
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</div>
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</div>
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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 /><br /></span><span style="color: #007700">function </span><span style="color: #0000BB">pick_server</span><span style="color: #007700">(</span><span style="color: #0000BB">$connected</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">, </span><span style="color: #0000BB">$master</span><span style="color: #007700">, </span><span style="color: #0000BB">$slaves</span><span style="color: #007700">, </span><span style="color: #0000BB">$last_used</span><span style="color: #007700">)<br />{<br /> static </span><span style="color: #0000BB">$slave_idx </span><span style="color: #007700">= </span><span style="color: #0000BB">0</span><span style="color: #007700">;<br /> static </span><span style="color: #0000BB">$num_slaves </span><span style="color: #007700">= </span><span style="color: #0000BB">NULL</span><span style="color: #007700">;<br /> if (</span><span style="color: #0000BB">is_null</span><span style="color: #007700">(</span><span style="color: #0000BB">$num_slaves</span><span style="color: #007700">))<br /> </span><span style="color: #0000BB">$num_slaves </span><span style="color: #007700">= </span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$slaves</span><span style="color: #007700">);<br /><br /> </span><span style="color: #FF8000">/* default: fallback to the plugins build-in logic */<br /> </span><span style="color: #0000BB">$ret </span><span style="color: #007700">= </span><span style="color: #0000BB">NULL</span><span style="color: #007700">;<br /><br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"User has connected to '%s'...\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$connected</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"... deciding where to run '%s'\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /><br /> </span><span style="color: #0000BB">$where </span><span style="color: #007700">= </span><span style="color: #0000BB">mysqlnd_ms_query_is_select</span><span style="color: #007700">(</span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /> switch (</span><span style="color: #0000BB">$where</span><span style="color: #007700">)<br /> {<br /> case </span><span style="color: #0000BB">MYSQLND_MS_QUERY_USE_MASTER</span><span style="color: #007700">:<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"... using master\n"</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">$ret </span><span style="color: #007700">= </span><span style="color: #0000BB">$master</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">];<br /> break;<br /> case </span><span style="color: #0000BB">MYSQLND_MS_QUERY_USE_SLAVE</span><span style="color: #007700">:<br /> </span><span style="color: #FF8000">/* SELECT or SQL hint for using slave */<br /> </span><span style="color: #007700">if (</span><span style="color: #0000BB">stristr</span><span style="color: #007700">(</span><span style="color: #0000BB">$query</span><span style="color: #007700">, </span><span style="color: #DD0000">"FROM table_on_slave_a_only"</span><span style="color: #007700">))<br /> {<br /> </span><span style="color: #FF8000">/* a table which is only on the first configured slave */<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"... access to table available only on slave A detected\n"</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">$ret </span><span style="color: #007700">= </span><span style="color: #0000BB">$slaves</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">];<br /> }<br /> else<br /> {<br /> </span><span style="color: #FF8000">/* round robin */<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"... some read-only query for a slave\n"</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">$ret </span><span style="color: #007700">= </span><span style="color: #0000BB">$slaves</span><span style="color: #007700">[</span><span style="color: #0000BB">$slave_idx</span><span style="color: #007700">++ % </span><span style="color: #0000BB">$num_slaves</span><span style="color: #007700">];<br /> }<br /> break;<br /> case </span><span style="color: #0000BB">MYSQLND_MS_QUERY_LAST_USED</span><span style="color: #007700">:<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"... using last used server\n"</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">$ret </span><span style="color: #007700">= </span><span style="color: #0000BB">$last_used</span><span style="color: #007700">;<br /> break;<br /> }<br /><br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"... ret = '%s'\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$ret</span><span style="color: #007700">);<br /> return </span><span style="color: #0000BB">$ret</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">mysqlnd_ms_set_user_pick_server</span><span style="color: #007700">(</span><span style="color: #DD0000">"pick_server"</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$mysqli </span><span style="color: #007700">= new </span><span style="color: #0000BB">mysqli</span><span style="color: #007700">(</span><span style="color: #DD0000">"myapp"</span><span style="color: #007700">, </span><span style="color: #DD0000">"root"</span><span style="color: #007700">, </span><span style="color: #DD0000">"root"</span><span style="color: #007700">, </span><span style="color: #DD0000">"test"</span><span style="color: #007700">);<br /><br />if (!(</span><span style="color: #0000BB">$res </span><span style="color: #007700">= </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT 1 FROM DUAL"</span><span style="color: #007700">)))<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"[%d] %s\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">errno</span><span style="color: #007700">, </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">error</span><span style="color: #007700">);<br />else<br /> </span><span style="color: #0000BB">$res</span><span style="color: #007700">-></span><span style="color: #0000BB">close</span><span style="color: #007700">();<br /><br />if (!(</span><span style="color: #0000BB">$res </span><span style="color: #007700">= </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT 2 FROM DUAL"</span><span style="color: #007700">)))<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"[%d] %s\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">errno</span><span style="color: #007700">, </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">error</span><span style="color: #007700">);<br />else<br /> </span><span style="color: #0000BB">$res</span><span style="color: #007700">-></span><span style="color: #0000BB">close</span><span style="color: #007700">();<br /><br /><br />if (!(</span><span style="color: #0000BB">$res </span><span style="color: #007700">= </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT * FROM table_on_slave_a_only"</span><span style="color: #007700">)))<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"[%d] %s\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">errno</span><span style="color: #007700">, </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">error</span><span style="color: #007700">);<br />else<br /> </span><span style="color: #0000BB">$res</span><span style="color: #007700">-></span><span style="color: #0000BB">close</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">close</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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User has connected to 'myapp'...
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... deciding where to run 'SELECT 1 FROM DUAL'
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... some read-only query for a slave
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... ret = 'tcp://192.168.2.27:3306'
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User has connected to 'myapp'...
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... deciding where to run 'SELECT 2 FROM DUAL'
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... some read-only query for a slave
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... ret = 'tcp://192.168.78.136:3306'
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User has connected to 'myapp'...
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... deciding where to run 'SELECT * FROM table_on_slave_a_only'
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... access to table available only on slave A detected
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... ret = 'tcp://192.168.2.27:3306'
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</pre></div>
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</div>
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</div>
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</p>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.mysqlnd-ms-set-user-pick-server-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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<span class="function"><a href="mysqlnd_ms_query_is_select.html" class="function" rel="rdfs-seeAlso">mysqlnd_ms_query_is_select()</a> - 查询给定的 SQL 会发送给 master、slave 还是最后使用的 MySQL server 执行。</span>
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</li>
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<li class="member">
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<a href="mysqlnd_ms.filter.html" class="link">Filter concept</a>
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</li>
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<li class="member">
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<a href="mysqlnd-ms.plugin-ini-json.html#ini.mysqlnd-ms-plugin-config-v2.filter-user" class="link"><em>user</em></a> filter
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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> |