S.H.I.E.L.D.
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<title>清空索引</title>
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<a href="http://www.xunsearch.com" target="_blank">Xunsearch PHP-SDK</a> v1.3.2 权威指南
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	<h1 id="-">清空索引</h1>

<p>当您的索引数据库发生了重大改变时必须清空索引。比如搜索项目的字段配置修改了，
或者是数据进行了大模迁移、导入或批量删除导致真实数据库和搜索数据库发生了较大的偏差。</p>

<blockquote class="tip">
<p><strong>Tip:</strong> 在我们附带的<a href="util.indexer.html">Indexer 索引管理工具</a>中提供了 <code>--clean</code> 
  选项用于清空项目的索引数据库，用起来更简洁。</p>
</blockquote>

<p>清空数据很简单，直接调用 <a href="../api/XSIndex.html#clean">XSIndex::clean</a> 即可，代码如下：</p>

<div class="hl-code"><div class="php-hl-main"><pre><span class="php-hl-comment">//</span><span class="php-hl-comment"> 执行清空操作</span>
<span class="php-hl-var">$index</span><span class="php-hl-code">-&gt;</span><span class="php-hl-identifier">clean</span><span class="php-hl-brackets">(</span><span class="php-hl-brackets">)</span><span class="php-hl-code">;
 
</span><span class="php-hl-comment">//</span><span class="php-hl-comment"> 重新加入文档数据</span><span class="php-hl-code">
...
</span><span class="php-hl-var">$index</span><span class="php-hl-code">-&gt;</span><span class="php-hl-identifier">add</span><span class="php-hl-brackets">(</span><span class="php-hl-var">$doc</span><span class="php-hl-brackets">)</span><span class="php-hl-code">;
...
</span><span class="php-hl-var">$index</span><span class="php-hl-code">-&gt;</span><span class="php-hl-identifier">add</span><span class="php-hl-brackets">(</span><span class="php-hl-var">$doc2</span><span class="php-hl-brackets">)</span><span class="php-hl-code">;
...</span></pre></div></div>

<blockquote class="note">
<p><strong>Note:</strong> 清空索引是一个同步操作，一旦执行立即生效，并且不可恢复。如果采用这种
  方式重建索引，由于原有索引被立即清空了，可能会有一小段时间无法搜索到数据。
  因此，如果您对线上项目操作，建议参见下一章节中介绍的平滑方式重建索引。</p>
</blockquote>

<div class="revision">$Id$</div>
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		<div class="prev"><a href="index.del.html">&laquo; 删除文档</a></div>
			<div class="next"><a href="index.rebuild.html">平滑重建索引 &raquo;</a></div>
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