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doc-exports/docs/dws/dev/dws_04_1412.html
luhuayi 177cd61a57 DWS DEVG 910.211 version 
Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com>
Co-authored-by: luhuayi <luhuayi@huawei.com>
Co-committed-by: luhuayi <luhuayi@huawei.com>
2025-05-05 07:44:03 +00:00

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<a name="EN-US_TOPIC_0000002046753925"></a><a name="EN-US_TOPIC_0000002046753925"></a>
<h1 class="topictitle1">PGXC_LWLOCKS</h1>
<div id="body0000002046753925"><p id="EN-US_TOPIC_0000002046753925__p10123542153713"><strong id="EN-US_TOPIC_0000002046753925__b4197161564811">PGXC_LWLOCK</strong> offers details on lightweight locks that are currently held or being waited for by all instances in the cluster. This view is supported only by 9.1.0.200 and later cluster versions.</p>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" id="EN-US_TOPIC_0000002046753925__table18928185635412" frame="border" border="1" rules="all"><caption><b>Table 1 </b>PGXC_LWLOCKS columns</caption><thead align="left"><tr id="EN-US_TOPIC_0000002046753925__row11928956125419"><th align="left" class="cellrowborder" valign="top" width="20.49204920492049%" id="mcps1.3.2.2.4.1.1"><p id="EN-US_TOPIC_0000002046753925__p49281956135417"><strong id="EN-US_TOPIC_0000002046753925__b185482294443813">Column</strong></p>
</th>
<th align="left" class="cellrowborder" valign="top" width="21.62216221622162%" id="mcps1.3.2.2.4.1.2"><p id="EN-US_TOPIC_0000002046753925__p39293566542"><strong id="EN-US_TOPIC_0000002046753925__b11781112813486">Type</strong></p>
</th>
<th align="left" class="cellrowborder" valign="top" width="57.88578857885789%" id="mcps1.3.2.2.4.1.3"><p id="EN-US_TOPIC_0000002046753925__p8929145613541"><strong id="EN-US_TOPIC_0000002046753925__b92764302486">Description</strong></p>
</th>
</tr>
</thead>
<tbody><tr id="EN-US_TOPIC_0000002046753925__row79290568549"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p29296564540">nodename</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p119291056195414">Name</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p69291556175414">Name of the node where the locked object resides</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002046753925__row5484528114311"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p8484228124313">pid</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p13484028154320">Bigint</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p548412874310">ID of the backend thread</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002046753925__row11446104920432"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p15446184916432">query_id</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p20446104974318">Bigint</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p3446449174316">ID of a query</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002046753925__row137071545445"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p1470714134414">lwtid</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p1170714174418">Integer</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p1970711413443">Lightweight thread ID of the backend thread</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002046753925__row773717141447"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p77371714114414">reqlockid</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p4737151464416">Integer</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p773731454413">ID of the lightweight lock that is being requested by the current thread</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002046753925__row37211192445"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p67212094441">reqlock</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p127211691442">Text</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p1172113994418">Name of the lightweight lock corresponding to <strong id="EN-US_TOPIC_0000002046753925__b18521191144916">reqlockid</strong></p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002046753925__row2761554204320"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p1676145416438">heldlocknums</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p176155494313">Integer</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p976195464319">Number of lightweight locks obtained by the current thread</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002046753925__row175710014418"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p1157120164412">heldlockid</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p65717044414">Integer</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p17571807449">Lightweight lock ID obtained by the current thread</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002046753925__row55295436438"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p7529164374320">heldlock</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p652914439439">Text</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p1321303717496">Name of the lightweight lock corresponding to <strong id="EN-US_TOPIC_0000002046753925__b191551226204914">heldlockid</strong></p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002046753925__row16370153714316"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002046753925__p437015379436">heldlockmode</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002046753925__p12370173717433">Text</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002046753925__p137033714313">Lightweight lock mode corresponding to <strong id="EN-US_TOPIC_0000002046753925__b11342183117496">heldlockid</strong></p>
</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="EN-US_TOPIC_0000002046753925__section1826671016191"><h4 class="sectiontitle">Example</h4><div class="p" id="EN-US_TOPIC_0000002046753925__en-us_topic_0000001666526750_p205031176173">Use the <strong id="EN-US_TOPIC_0000002046753925__b771945785111">PGXC_LWLOCKS</strong> view to get details on lightweight locks that are currently held or being waited for by all instances in the cluster.<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000002046753925__en-us_topic_0000001666526750_screen34889521162"><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></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">pgxc_lwlocks</span><span class="p">;</span>
<span class="w"> </span><span class="n">nodename</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">query_id</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">lwtid</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">reqlockid</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">reqlock</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">heldlocknums</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">heldlockid</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">heldlock</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">heldlockmode</span>
<span class="c1">-----------+-----------------+-------------------+-------+-----------+---------+--------------+------------+--------------------+--------------</span>
<span class="w"> </span><span class="n">datanode1</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">139810224193360</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">78250043525924188</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">54844</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">76390</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">BUFFER_POOL_LWLOCK</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">Shared</span>
<span class="w"> </span><span class="n">datanode1</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">139810224198200</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">78250043525924886</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">54922</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">957438</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">PGPROC_LWLOCK</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="k">Exclusive</span>
<span class="w"> </span><span class="n">datanode2</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">140262654050288</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">54832</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">7</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">WALWriteLock</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="k">Exclusive</span>
<span class="w"> </span><span class="n">datanode2</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">140262654052488</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">78250043525923195</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">54847</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">15862</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">BUFFER_POOL_LWLOCK</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">Shared</span>
<span class="p">(</span><span class="mi">4</span><span class="w"> </span><span class="k">rows</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
</div>
</div>
<div>
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<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_04_0639.html">System Views</a></div>
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