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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_0000001188110546"></a><a name="EN-US_TOPIC_0000001188110546"></a>
<h1 class="topictitle1">Server Signaling Functions</h1>
<div id="body1553151203303"><p id="EN-US_TOPIC_0000001188110546__ab3c76df4dd9a46b18421b9cf63db958b">Server signaling functions send control signals to other server processes. Only system administrators can use these functions.</p>
<div class="section" id="EN-US_TOPIC_0000001188110546__section20902121511710"><h4 class="sectiontitle">pg_cancel_backend(pid int)</h4><p id="EN-US_TOPIC_0000001188110546__p1697164012719">Description: Cancels a current query of the backend.</p>
<p id="EN-US_TOPIC_0000001188110546__p1269914019717">Return type: <span id="EN-US_TOPIC_0000001188110546__text2262153814228">boolean</span></p>
<p id="EN-US_TOPIC_0000001188110546__p1070019401978">Note: <strong id="EN-US_TOPIC_0000001188110546__b1764020316613">pg_cancel_backend</strong> sends a query cancellation signal (<strong id="EN-US_TOPIC_0000001188110546__b136471031363">SIGINT</strong>) to the backend process identified by <strong id="EN-US_TOPIC_0000001188110546__b20649531966">pid</strong>. The PID of an active backend process can be found in the <strong id="EN-US_TOPIC_0000001188110546__b179712181793829">pid</strong> column of the <strong id="EN-US_TOPIC_0000001188110546__b151803767693829">pg_stat_activity</strong> view, or can be found by listing the database process using <strong id="EN-US_TOPIC_0000001188110546__b204500080893829">ps</strong> on the server.</p>
<p id="EN-US_TOPIC_0000001188110546__p106968145309">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001188110546__screen696052093413"><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>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">pg_stat_activity</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">stmt_type</span><span class="w"> </span><span class="o">=</span><span class="s1">'RESET'</span><span class="p">;</span>
<span class="w"> </span><span class="n">pid</span>
<span class="c1">-----------------</span>
<span class="w"> </span><span class="mi">281471222065200</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
<span class="k">SELECT</span><span class="w"> </span><span class="n">pg_cancel_backend</span><span class="p">(</span><span class="mi">281471222065200</span><span class="p">);</span>
<span class="w"> </span><span class="n">pg_cancel_backend</span>
<span class="c1">-------------------</span>
<span class="w"> </span><span class="n">t</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001188110546__section1421341981215"><h4 class="sectiontitle">pg_reload_conf()</h4><p id="EN-US_TOPIC_0000001188110546__p67044406713">Description: Notifies the server process to reload the configuration file.</p>
<p id="EN-US_TOPIC_0000001188110546__p570510402711">Return type: <span id="EN-US_TOPIC_0000001188110546__text563113932217">boolean</span></p>
<p id="EN-US_TOPIC_0000001188110546__p770610401671">Note: <strong id="EN-US_TOPIC_0000001188110546__b195811718114319">pg_reload_conf</strong> sends a <strong id="EN-US_TOPIC_0000001188110546__b32242014165">SIGHUP</strong> signal to the server. As a result, all server processes reload their configuration files.</p>
<p id="EN-US_TOPIC_0000001188110546__p18366191283216">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001188110546__screen4366121223212"><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>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">pg_reload_conf</span><span class="p">();</span>
<span class="w"> </span><span class="n">pg_reload_conf</span>
<span class="c1">----------------</span>
<span class="w"> </span><span class="n">t</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001188110546__section11158638161318"><h4 class="sectiontitle">pg_rotate_logfile()</h4><p id="EN-US_TOPIC_0000001188110546__p17101540075">Description: Rotates the log files of the server.</p>
<p id="EN-US_TOPIC_0000001188110546__p671134012718">Return type: <span id="EN-US_TOPIC_0000001188110546__text13720153914223">boolean</span></p>
<p id="EN-US_TOPIC_0000001188110546__p071313407716">Note: pg_rotate_logfile instructs the log file manager to immediately switch to a new output file. This function is valid only if the built-in log collector is running.</p>
<p id="EN-US_TOPIC_0000001188110546__p14922714719">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001188110546__screen5338164013717"><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>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">pg_rotate_logfile</span><span class="p">();</span>
<span class="w"> </span><span class="n">pg_rotate_logfile</span>
<span class="c1">-------------------</span>
<span class="w"> </span><span class="n">t</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001188110546__section859575811132"><h4 class="sectiontitle">pg_terminate_backend(pid int)</h4><p id="EN-US_TOPIC_0000001188110546__p371617401778">Description: Terminates a backend thread.</p>
<p id="EN-US_TOPIC_0000001188110546__p15717340875">Return type: <span id="EN-US_TOPIC_0000001188110546__text194733409227">boolean</span></p>
<p id="EN-US_TOPIC_0000001188110546__p17191840877">Note: Each of these functions returns <strong id="EN-US_TOPIC_0000001188110546__en-us_topic_0058965547_b84235270692911">true</strong> if they are successful and <strong id="EN-US_TOPIC_0000001188110546__en-us_topic_0058965547_b84235270692917">false</strong> otherwise.</p>
<p id="EN-US_TOPIC_0000001188110546__p117208401676">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001188110546__screen672114015716"><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>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span>
<span class="normal">13</span>
<span class="normal">14</span>
<span class="normal">15</span>
<span class="normal">16</span>
<span class="normal">17</span>
<span class="normal">18</span>
<span class="normal">19</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">pg_stat_activity</span><span class="p">;</span>
<span class="w"> </span><span class="n">pid</span><span class="w"> </span>
<span class="c1">-----------------</span>
<span class="w"> </span><span class="mi">140657876268816</span>
<span class="w"> </span><span class="mi">140433774061312</span>
<span class="w"> </span><span class="mi">140433587902208</span>
<span class="w"> </span><span class="mi">140433656592128</span>
<span class="w"> </span><span class="mi">140433723717376</span>
<span class="w"> </span><span class="mi">140433637189376</span>
<span class="w"> </span><span class="mi">140433552770816</span>
<span class="w"> </span><span class="mi">140433481983744</span>
<span class="w"> </span><span class="mi">140433349310208</span>
<span class="p">(</span><span class="mi">9</span><span class="w"> </span><span class="k">rows</span><span class="p">)</span>
<span class="k">SELECT</span><span class="w"> </span><span class="n">pg_terminate_backend</span><span class="p">(</span><span class="mi">140657876268816</span><span class="p">);</span>
<span class="w"> </span><span class="n">pg_terminate_backend</span><span class="w"> </span>
<span class="c1">----------------------</span>
<span class="w"> </span><span class="n">t</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001188110546__section198745281411"><h4 class="sectiontitle">pg_wlm_jump_queue(pid int)</h4><p id="EN-US_TOPIC_0000001188110546__p1975519401873">Description: Moves a task to the top of the CN queue.</p>
<p id="EN-US_TOPIC_0000001188110546__p18757184017717">Return type: Boolean</p>
<p id="EN-US_TOPIC_0000001188110546__p67581405716">Note: Each of these functions returns <strong id="EN-US_TOPIC_0000001188110546__b33084189">true</strong> if they are successful and <strong id="EN-US_TOPIC_0000001188110546__b1292822771">false</strong> otherwise.</p>
<p id="EN-US_TOPIC_0000001188110546__p13318132219167">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001188110546__screen4845174931619"><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>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">pg_stat_activity</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">stmt_type</span><span class="w"> </span><span class="o">=</span><span class="s1">'RESET'</span><span class="p">;</span>
<span class="w"> </span><span class="n">pid</span>
<span class="c1">-----------------</span>
<span class="w"> </span><span class="mi">281471222065200</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
<span class="k">SELECT</span><span class="w"> </span><span class="n">pg_wlm_jump_queue</span><span class="p">(</span><span class="mi">281471222065200</span><span class="p">);</span>
<span class="w"> </span><span class="n">pg_wlm_jump_queue</span>
<span class="c1">-------------------</span>
<span class="w"> </span><span class="n">t</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001188110546__section634413011151"><h4 class="sectiontitle">gs_wlm_switch_cgroup(pid int, cgroup text)</h4><p id="EN-US_TOPIC_0000001188110546__p17624407720">Description: Moves a job to other Cgroup to improve the job priority.</p>
<p id="EN-US_TOPIC_0000001188110546__p167633401712">Return type: Boolean</p>
<p id="EN-US_TOPIC_0000001188110546__p1764240672">Note: Each of these functions returns <strong id="EN-US_TOPIC_0000001188110546__b513995033">true</strong> if they are successful and <strong id="EN-US_TOPIC_0000001188110546__b1403191137">false</strong> otherwise.</p>
</div>
<div class="section" id="EN-US_TOPIC_0000001188110546__section19503121051718"><h4 class="sectiontitle">pg_cancel_query(queryId int)</h4><p id="EN-US_TOPIC_0000001188110546__p376714019720">Description: Cancels a current query of the backend. This function is supported in 8.1.2 or later.</p>
<p id="EN-US_TOPIC_0000001188110546__p1476914017720">Return type: <span id="EN-US_TOPIC_0000001188110546__text424454210347">boolean</span></p>
<p id="EN-US_TOPIC_0000001188110546__p1177013401778">Note: <strong id="EN-US_TOPIC_0000001188110546__b1958256164212">pg_cancel_query</strong> sends a query cancellation signal (<strong id="EN-US_TOPIC_0000001188110546__b10720922518">SIGINT</strong>) to the backend process identified by <strong id="EN-US_TOPIC_0000001188110546__b1558376144213">query_id</strong>. The <strong id="EN-US_TOPIC_0000001188110546__b53507886293829">query_id</strong> of an active backend process can be found in the <strong id="EN-US_TOPIC_0000001188110546__b126110395593829">query_id</strong> column of the <strong id="EN-US_TOPIC_0000001188110546__b170899393993829">pg_stat_activity</strong> view.</p>
<p id="EN-US_TOPIC_0000001188110546__p2143112672119">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001188110546__screen2648174912115"><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>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">query_id</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">pgxc_stat_activity</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">stmt_type</span><span class="w"> </span><span class="o">=</span><span class="s1">'RESET'</span><span class="p">;</span>
<span class="w"> </span><span class="n">query_id</span>
<span class="c1">----------</span>
<span class="w"> </span><span class="mi">0</span>
<span class="w"> </span><span class="mi">0</span>
<span class="p">(</span><span class="mi">2</span><span class="w"> </span><span class="k">rows</span><span class="p">)</span>
<span class="k">SELECT</span><span class="w"> </span><span class="n">pg_cancel_query</span><span class="p">(</span><span class="mi">0</span><span class="p">);</span>
<span class="w"> </span><span class="n">pg_cancel_query</span>
<span class="c1">-----------------</span>
<span class="w"> </span><span class="n">f</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001188110546__section42513316177"><h4 class="sectiontitle">pgxc_cancel_query(queryId int)</h4><p id="EN-US_TOPIC_0000001188110546__p1177464018720">Description: Cancels the query that is being executed in the current cluster. This function is supported in 8.1.2 or later.</p>
<p id="EN-US_TOPIC_0000001188110546__p577517401275">Return type: <span id="EN-US_TOPIC_0000001188110546__text205541231205116">boolean</span></p>
<p id="EN-US_TOPIC_0000001188110546__p1577614401873">Note: If the queries of all nodes have been canceled, <strong id="EN-US_TOPIC_0000001188110546__b45528024193829">true</strong> is returned. Otherwise, <strong id="EN-US_TOPIC_0000001188110546__b180016603893829">false</strong> is returned.</p>
<p id="EN-US_TOPIC_0000001188110546__p5544108132315">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001188110546__screen163032480349"><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>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">query_id</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">pgxc_stat_activity</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">stmt_type</span><span class="w"> </span><span class="o">=</span><span class="s1">'RESET'</span><span class="p">;</span>
<span class="w"> </span><span class="n">query_id</span>
<span class="c1">----------</span>
<span class="w"> </span><span class="mi">0</span>
<span class="w"> </span><span class="mi">0</span>
<span class="p">(</span><span class="mi">2</span><span class="w"> </span><span class="k">rows</span><span class="p">)</span>
<span class="k">SELECT</span><span class="w"> </span><span class="n">pgxc_cancel_query</span><span class="p">(</span><span class="mi">0</span><span class="p">);</span>
<span class="w"> </span><span class="n">pgxc_cancel_query</span>
<span class="c1">-------------------</span>
<span class="w"> </span><span class="n">f</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001188110546__section1536411483175"><h4 class="sectiontitle">pg_terminate_query(queryId int)</h4><p id="EN-US_TOPIC_0000001188110546__p678044019715">Description: Terminates a current query of the backend. This function is supported in 8.1.2 or later.</p>
<p id="EN-US_TOPIC_0000001188110546__p5781940775">Return type: <span id="EN-US_TOPIC_0000001188110546__text57614331519">boolean</span></p>
<p id="EN-US_TOPIC_0000001188110546__p11918412143711">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001188110546__screen15822154823715"><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>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">query_id</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">pgxc_stat_activity</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">stmt_type</span><span class="w"> </span><span class="o">=</span><span class="s1">'RESET'</span><span class="p">;</span>
<span class="w"> </span><span class="n">query_id</span>
<span class="c1">----------</span>
<span class="w"> </span><span class="mi">0</span>
<span class="w"> </span><span class="mi">0</span>
<span class="p">(</span><span class="mi">2</span><span class="w"> </span><span class="k">rows</span><span class="p">)</span>
<span class="k">SELECT</span><span class="w"> </span><span class="n">pg_terminate_query</span><span class="p">(</span><span class="mi">0</span><span class="p">);</span>
<span class="w"> </span><span class="n">pg_terminate_query</span>
<span class="c1">--------------------</span>
<span class="w"> </span><span class="n">f</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001188110546__section1966853711312"><h4 class="sectiontitle">pgxc_terminate_query(queryId int)</h4><p id="EN-US_TOPIC_0000001188110546__p1366783771315">Description: Terminates the query that is being executed in the current cluster. This function is supported in 8.1.2 or later.</p>
<p id="EN-US_TOPIC_0000001188110546__p1466773771310">Return type: <span id="EN-US_TOPIC_0000001188110546__text612441011">boolean</span></p>
<p id="EN-US_TOPIC_0000001188110546__p766718379133">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001188110546__screen106681037171319"><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>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">query_id</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">pgxc_stat_activity</span><span class="p">;</span>
<span class="w"> </span><span class="n">query_id</span><span class="w"> </span>
<span class="c1">-----------------</span>
<span class="w"> </span><span class="mi">72339069014638631</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">rows</span><span class="p">)</span>
<span class="k">SELECT</span><span class="w"> </span><span class="n">pgxc_terminate_query</span><span class="p">(</span><span class="mi">72339069014638631</span><span class="p">);</span>
<span class="w"> </span><span class="n">pgxc_terminate_query</span><span class="w"> </span>
<span class="c1">----------------------</span>
<span class="w"> </span><span class="n">t</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</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_0052.html">System Administration Functions</a></div>
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