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doc-exports/docs/dws/dev/dws_04_1411.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_0000002021921864"></a><a name="EN-US_TOPIC_0000002021921864"></a>
<h1 class="topictitle1">PG_LWLOCKS</h1>
<div id="body0000002021921864"><p id="EN-US_TOPIC_0000002021921864__p117072389515"><strong id="EN-US_TOPIC_0000002021921864__b4878144273010">PG_LWLOCKS</strong> provides information on lightweight locks currently held or being waited for by the current instance. 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_0000002021921864__table970733875113" frame="border" border="1" rules="all"><caption><b>Table 1 </b>PG_LWLOCKS columns</caption><thead align="left"><tr id="EN-US_TOPIC_0000002021921864__row47072381514"><th align="left" class="cellrowborder" valign="top" width="20.49204920492049%" id="mcps1.3.2.2.4.1.1"><p id="EN-US_TOPIC_0000002021921864__p1170763865110"><strong id="EN-US_TOPIC_0000002021921864__b173778822543653">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_0000002021921864__p57071438135119"><strong id="EN-US_TOPIC_0000002021921864__b4981205511303">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_0000002021921864__p570816380514"><strong id="EN-US_TOPIC_0000002021921864__b1082717569307">Description</strong></p>
</th>
</tr>
</thead>
<tbody><tr id="EN-US_TOPIC_0000002021921864__row1370893865112"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002021921864__p17081738105114">pid</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002021921864__p470833875113">Bigint</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002021921864__p1870812382513">ID of the backend thread.</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002021921864__row1570815389516"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002021921864__p9708338115119">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_0000002021921864__p16708183814510">Bigint</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002021921864__p1470812383519">ID of a query.</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002021921864__row19708638145112"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002021921864__p20708138165110">lwtid</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002021921864__p127089386514">Integer</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002021921864__p170811385511">Lightweight thread ID of the backend thread.</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002021921864__row1170819388511"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002021921864__p770953815516">reqlockid</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002021921864__p197094384514">Integer</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002021921864__p20709193855115">ID of the lightweight lock that is being requested by the current thread.</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002021921864__row1709203817513"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002021921864__p11709638145111">reqlock</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002021921864__p14709163875120">Text</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002021921864__p77091238105115">Name of the lightweight lock corresponding to <strong id="EN-US_TOPIC_0000002021921864__b2440107203314">reqlockid</strong>.</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002021921864__row1970963819513"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002021921864__p6709103885114">heldlocknums</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002021921864__p1770933813516">Integer</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002021921864__p6709838135115">Number of lightweight locks obtained by the current thread.</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002021921864__row1170983815115"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002021921864__p11709133812519">heldlockid</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002021921864__p1470910389511">Integer</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002021921864__p8709193845117">Lightweight lock ID obtained by the current thread.</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002021921864__row6709183811518"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002021921864__p9710938105114">heldlock</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002021921864__p671016383517">Text</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002021921864__p7710103875118">Name of the lightweight lock corresponding to <strong id="EN-US_TOPIC_0000002021921864__b193721840183812">heldlockid</strong>.</p>
</td>
</tr>
<tr id="EN-US_TOPIC_0000002021921864__row971012383512"><td class="cellrowborder" valign="top" width="20.49204920492049%" headers="mcps1.3.2.2.4.1.1 "><p id="EN-US_TOPIC_0000002021921864__p0710163825110">heldlockmode</p>
</td>
<td class="cellrowborder" valign="top" width="21.62216221622162%" headers="mcps1.3.2.2.4.1.2 "><p id="EN-US_TOPIC_0000002021921864__p19710103819513">Text</p>
</td>
<td class="cellrowborder" valign="top" width="57.88578857885789%" headers="mcps1.3.2.2.4.1.3 "><p id="EN-US_TOPIC_0000002021921864__p571013385516">Lightweight lock mode corresponding to <strong id="EN-US_TOPIC_0000002021921864__b202041250163811">heldlockid</strong>.</p>
</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="EN-US_TOPIC_0000002021921864__section1826671016191"><h4 class="sectiontitle">Example</h4><div class="p" id="EN-US_TOPIC_0000002021921864__en-us_topic_0000001666526750_p205031176173">Use the <strong id="EN-US_TOPIC_0000002021921864__b59841471602">PG_LWLOCKS</strong> view to query information about lightweight locks that are being held or waiting for the current instance.<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000002021921864__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></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">pg_lwlocks</span><span class="p">;</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="mi">139810224192480</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">54842</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="mi">139810224199520</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">78250043526306022</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">54963</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">193860</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="k">Exclusive</span>
<span class="p">(</span><span class="mi">2</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>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_04_0639.html">System Views</a></div>
</div>
</div>
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