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Lu, Huayi e6fa411af0 DWS DEV 830.201 version 
Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com>
Co-authored-by: Lu, Huayi <luhuayi@huawei.com>
Co-committed-by: Lu, Huayi <luhuayi@huawei.com>
2024-05-16 07:24:04 +00:00

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<a name="EN-US_TOPIC_0000001233430181"></a><a name="EN-US_TOPIC_0000001233430181"></a>
<h1 class="topictitle1">CLEAN CONNECTION</h1>
<div id="body8662426"><div class="section" id="EN-US_TOPIC_0000001233430181__s61b3750edf864fe9b264d8276ff2ac0a"><h4 class="sectiontitle">Function</h4><p id="EN-US_TOPIC_0000001233430181__a7b54fad2ac3c4c3da9174de9c2f2fc60"><strong id="EN-US_TOPIC_0000001233430181__b41903309392414">CLEAN CONNECTION</strong> clears database connections when a database is abnormal. You may use this statement to delete a specific user's connections to a specified database.</p>
</div>
<div class="section" id="EN-US_TOPIC_0000001233430181__s3e1e2127ad7a48b88be58daa90e5b30b"><h4 class="sectiontitle">Precautions</h4><p id="EN-US_TOPIC_0000001233430181__a823e4d9b0e464c3fb52135f337486f30">None</p>
</div>
<div class="section" id="EN-US_TOPIC_0000001233430181__s7e91f65b5e2e407b994d67cc3a87b8d9"><h4 class="sectiontitle">Syntax</h4><div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001233430181__sb6554bfd6d6848069258ef6fb691a4c2"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span></pre></div></td><td class="code"><div><pre><span></span><span class="n">CLEAN</span><span class="w"> </span><span class="k">CONNECTION</span><span class="w"> </span>
<span class="w"> </span><span class="k">TO</span><span class="w"> </span><span class="err">{</span><span class="w"> </span><span class="n">COORDINATOR</span><span class="w"> </span><span class="p">(</span><span class="w"> </span><span class="n">nodename</span><span class="w"> </span><span class="p">[,</span><span class="w"> </span><span class="p">...</span><span class="w"> </span><span class="p">]</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">NODE</span><span class="w"> </span><span class="p">(</span><span class="w"> </span><span class="n">nodename</span><span class="w"> </span><span class="p">[,</span><span class="w"> </span><span class="p">...</span><span class="w"> </span><span class="p">]</span><span class="w"> </span><span class="p">)</span><span class="o">|</span><span class="w"> </span><span class="k">ALL</span><span class="w"> </span><span class="p">[</span><span class="w"> </span><span class="k">CHECK</span><span class="w"> </span><span class="p">]</span><span class="w"> </span><span class="p">[</span><span class="w"> </span><span class="k">FORCE</span><span class="w"> </span><span class="p">]</span><span class="w"> </span><span class="err">}</span>
<span class="w"> </span><span class="p">[</span><span class="w"> </span><span class="k">FOR</span><span class="w"> </span><span class="k">DATABASE</span><span class="w"> </span><span class="n">dbname</span><span class="w"> </span><span class="p">]</span><span class="w"> </span>
<span class="w"> </span><span class="p">[</span><span class="w"> </span><span class="k">TO</span><span class="w"> </span><span class="k">USER</span><span class="w"> </span><span class="n">username</span><span class="w"> </span><span class="p">];</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001233430181__sd0697749ee8f434db895b86971ef673a"><h4 class="sectiontitle">Parameter Description</h4><ul id="EN-US_TOPIC_0000001233430181__u80866fce7a4149cf8406007dd2e69b56"><li id="EN-US_TOPIC_0000001233430181__l52ce5c2ebf1b44aab1d3abd64df21a4d"><strong id="EN-US_TOPIC_0000001233430181__af212631f921a4dff89a4443bf26d75ff">CHECK</strong><p id="EN-US_TOPIC_0000001233430181__a998243338323406eae23452a987cc696">This parameter can be specified only when the node list is specified as <strong id="EN-US_TOPIC_0000001233430181__b84235270616436">TO ALL</strong>. Setting this parameter will check whether a database is accessed by other sessions before its connections are cleared. If any sessions are detected before <strong id="EN-US_TOPIC_0000001233430181__b84235270616506">DROP DATABASE</strong> is executed, an error will be reported and the database will not be deleted.</p>
</li><li id="EN-US_TOPIC_0000001233430181__lef6e69c8cdf846f3ab124ce1549d66ea"><strong id="EN-US_TOPIC_0000001233430181__adcdf83e210f148aab88a74df64734444">FORCE</strong><p id="EN-US_TOPIC_0000001233430181__en-us_topic_0059779089_p293893410336">This parameter can be specified only when the node list is specified as <strong id="EN-US_TOPIC_0000001233430181__b105812337816516">TO ALL</strong>. Setting this parameter will send SIGTERM signals to all the threads related to the specified <strong id="EN-US_TOPIC_0000001233430181__b842352706165216">dbname</strong> and <strong id="EN-US_TOPIC_0000001233430181__b842352706165219">username</strong> and forcibly shut them down.</p>
</li><li id="EN-US_TOPIC_0000001233430181__l5df6483f095b48ddb7eea594ac2a60db"><strong id="EN-US_TOPIC_0000001233430181__aad520db2153b43e29ff56b6411ada64f">COORDINATOR ( nodename [, ... ] ) | NODE ( nodename [, ... ] ) | ALL</strong><p id="EN-US_TOPIC_0000001233430181__aec3073565c60407dbcc2190e2286580e">Deletes connections on a specified node. There are three scenarios:</p>
<ul id="EN-US_TOPIC_0000001233430181__u08750c2e0429434a90b1fba7981cf7de"><li id="EN-US_TOPIC_0000001233430181__l847d3d6481b84571917557dcd1b9ff89">Deletes connections to a specified CN.</li><li id="EN-US_TOPIC_0000001233430181__l818b4f7c689b418cb0c1d5b24d51aa5e">Deletes connections to a specified DN.</li><li id="EN-US_TOPIC_0000001233430181__lc7ec667a44fa48e2a377785152b5780e">Deletes connections to all CNs and DNs.</li></ul>
<p id="EN-US_TOPIC_0000001233430181__a62f8a5f5bc6e4dd69e2f6c22bf70f5b4">Value range: <strong id="EN-US_TOPIC_0000001233430181__b6063514091235">nodename</strong> is an existing node name.</p>
</li><li id="EN-US_TOPIC_0000001233430181__l19b695b153794959b4418564303dd074"><strong id="EN-US_TOPIC_0000001233430181__aef869649a322477fb6f1a914133886a0">dbname</strong><p id="EN-US_TOPIC_0000001233430181__ab5412b91286e40dfa878c45bb6394a5d">Deletes connections to a specific database. If this parameter is not specified, connections to all databases will be deleted.</p>
<p id="EN-US_TOPIC_0000001233430181__a9634df102517425fb9a56c004aadcd03">Value range: an existing database name</p>
</li><li id="EN-US_TOPIC_0000001233430181__l710aa1cd6bda4383b8f55deafe0e85ab"><strong id="EN-US_TOPIC_0000001233430181__a3459a78860e34ffa9082cf04e303309a">username</strong><p id="EN-US_TOPIC_0000001233430181__ae3434a884d944cbaa0769bf552c8f263">Deletes connections of a specific user. If this parameter is not specified, connections of all users will be deleted.</p>
<p id="EN-US_TOPIC_0000001233430181__a7b7b5b5046114ae781047f658ebf0897">Value range: an existing user name</p>
<div class="note" id="EN-US_TOPIC_0000001233430181__note134294283812"><img src="public_sys-resources/note_3.0-en-us.png"><span class="notetitle"> </span><div class="notebody"><p id="EN-US_TOPIC_0000001233430181__p3429192133812">Either <strong id="EN-US_TOPIC_0000001233430181__b1431114312469">dbname</strong> or <strong id="EN-US_TOPIC_0000001233430181__b113021720143714">username</strong> must be specified.</p>
</div></div>
</li></ul>
</div>
<div class="section" id="EN-US_TOPIC_0000001233430181__s32c27b0e6f754340bada174a83e77b45"><h4 class="sectiontitle">Examples</h4><p id="EN-US_TOPIC_0000001233430181__p133841604282">Clean connections to nodes dn1 and dn2 for the <strong id="EN-US_TOPIC_0000001233430181__b21156466333418">template1</strong> database.</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001233430181__screen0928125117283"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span></pre></div></td><td class="code"><div><pre><span></span><span class="n">CLEAN</span><span class="w"> </span><span class="k">CONNECTION</span><span class="w"> </span><span class="k">TO</span><span class="w"> </span><span class="n">NODE</span><span class="w"> </span><span class="p">(</span><span class="n">dn1</span><span class="p">,</span><span class="n">dn2</span><span class="p">)</span><span class="w"> </span><span class="k">FOR</span><span class="w"> </span><span class="k">DATABASE</span><span class="w"> </span><span class="n">template1</span><span class="p">;</span>
</pre></div></td></tr></table></div>
</div>
<p id="EN-US_TOPIC_0000001233430181__p13384190142819">Clean user <strong id="EN-US_TOPIC_0000001233430181__b128523346833418">jack</strong>'s connections to dn1.</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001233430181__screen19469124882810"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span></pre></div></td><td class="code"><div><pre><span></span><span class="n">CLEAN</span><span class="w"> </span><span class="k">CONNECTION</span><span class="w"> </span><span class="k">TO</span><span class="w"> </span><span class="n">NODE</span><span class="w"> </span><span class="p">(</span><span class="n">dn1</span><span class="p">)</span><span class="w"> </span><span class="k">TO</span><span class="w"> </span><span class="k">USER</span><span class="w"> </span><span class="n">jack</span><span class="p">;</span>
</pre></div></td></tr></table></div>
</div>
<p id="EN-US_TOPIC_0000001233430181__p1938415015287">Delete all connections to the <strong id="EN-US_TOPIC_0000001233430181__b139787381833418"></strong><strong id="EN-US_TOPIC_0000001233430181__b125040633833418"><span id="EN-US_TOPIC_0000001233430181__text438410112816">gaussdb</span></strong> database.</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001233430181__screen1275754415283"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span></pre></div></td><td class="code"><div><pre><span></span><span class="n">CLEAN</span><span class="w"> </span><span class="k">CONNECTION</span><span class="w"> </span><span class="k">TO</span><span class="w"> </span><span class="k">ALL</span><span class="w"> </span><span class="k">FORCE</span><span class="w"> </span><span class="k">FOR</span><span class="w"> </span><span class="k">DATABASE</span><span class="w"> </span><span class="n">gaussdb</span><span class="p">;</span>
</pre></div></td></tr></table></div>
</div>
</div>
</div>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_06_0118.html">DDL Syntax</a></div>
</div>
</div>
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