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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 12:15:05 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 12:15:05 +0000
commit46651ce6fe013220ed397add242004d764fc0153 (patch)
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downloadpostgresql-14-46651ce6fe013220ed397add242004d764fc0153.tar.xz
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Adding upstream version 14.5.upstream/14.5upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>20.12. Lock Management</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="runtime-config-client.html" title="20.11. Client Connection Defaults" /><link rel="next" href="runtime-config-compatible.html" title="20.13. Version and Platform Compatibility" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">20.12. Lock Management</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="runtime-config-client.html" title="20.11. Client Connection Defaults">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="runtime-config.html" title="Chapter 20. Server Configuration">Up</a></td><th width="60%" align="center">Chapter 20. Server Configuration</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="runtime-config-compatible.html" title="20.13. Version and Platform Compatibility">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="RUNTIME-CONFIG-LOCKS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">20.12. Lock Management</h2></div></div></div><div class="variablelist"><dl class="variablelist"><dt id="GUC-DEADLOCK-TIMEOUT"><span class="term"><code class="varname">deadlock_timeout</code> (<code class="type">integer</code>)
+ <a id="id-1.6.7.15.2.1.1.3" class="indexterm"></a>
+ <a id="id-1.6.7.15.2.1.1.4" class="indexterm"></a>
+ <a id="id-1.6.7.15.2.1.1.5" class="indexterm"></a>
+ </span></dt><dd><p>
+ This is the amount of time to wait on a lock
+ before checking to see if there is a deadlock condition. The
+ check for deadlock is relatively expensive, so the server doesn't run
+ it every time it waits for a lock. We optimistically assume
+ that deadlocks are not common in production applications and
+ just wait on the lock for a while before checking for a
+ deadlock. Increasing this value reduces the amount of time
+ wasted in needless deadlock checks, but slows down reporting of
+ real deadlock errors.
+ If this value is specified without units, it is taken as milliseconds.
+ The default is one second (<code class="literal">1s</code>),
+ which is probably about the smallest value you would want in
+ practice. On a heavily loaded server you might want to raise it.
+ Ideally the setting should exceed your typical transaction time,
+ so as to improve the odds that a lock will be released before
+ the waiter decides to check for deadlock. Only superusers can change
+ this setting.
+ </p><p>
+ When <a class="xref" href="runtime-config-logging.html#GUC-LOG-LOCK-WAITS">log_lock_waits</a> is set,
+ this parameter also determines the amount of time to wait before
+ a log message is issued about the lock wait. If you are trying
+ to investigate locking delays you might want to set a shorter than
+ normal <code class="varname">deadlock_timeout</code>.
+ </p></dd><dt id="GUC-MAX-LOCKS-PER-TRANSACTION"><span class="term"><code class="varname">max_locks_per_transaction</code> (<code class="type">integer</code>)
+ <a id="id-1.6.7.15.2.2.1.3" class="indexterm"></a>
+ </span></dt><dd><p>
+ The shared lock table tracks locks on
+ <code class="varname">max_locks_per_transaction</code> * (<a class="xref" href="runtime-config-connection.html#GUC-MAX-CONNECTIONS">max_connections</a> + <a class="xref" href="runtime-config-resource.html#GUC-MAX-PREPARED-TRANSACTIONS">max_prepared_transactions</a>) objects (e.g., tables);
+ hence, no more than this many distinct objects can be locked at
+ any one time. This parameter controls the average number of object
+ locks allocated for each transaction; individual transactions
+ can lock more objects as long as the locks of all transactions
+ fit in the lock table. This is <span class="emphasis"><em>not</em></span> the number of
+ rows that can be locked; that value is unlimited. The default,
+ 64, has historically proven sufficient, but you might need to
+ raise this value if you have queries that touch many different
+ tables in a single transaction, e.g., query of a parent table with
+ many children. This parameter can only be set at server start.
+ </p><p>
+ When running a standby server, you must set this parameter to the
+ same or higher value than on the primary server. Otherwise, queries
+ will not be allowed in the standby server.
+ </p></dd><dt id="GUC-MAX-PRED-LOCKS-PER-TRANSACTION"><span class="term"><code class="varname">max_pred_locks_per_transaction</code> (<code class="type">integer</code>)
+ <a id="id-1.6.7.15.2.3.1.3" class="indexterm"></a>
+ </span></dt><dd><p>
+ The shared predicate lock table tracks locks on
+ <code class="varname">max_pred_locks_per_transaction</code> * (<a class="xref" href="runtime-config-connection.html#GUC-MAX-CONNECTIONS">max_connections</a> + <a class="xref" href="runtime-config-resource.html#GUC-MAX-PREPARED-TRANSACTIONS">max_prepared_transactions</a>) objects (e.g., tables);
+ hence, no more than this many distinct objects can be locked at
+ any one time. This parameter controls the average number of object
+ locks allocated for each transaction; individual transactions
+ can lock more objects as long as the locks of all transactions
+ fit in the lock table. This is <span class="emphasis"><em>not</em></span> the number of
+ rows that can be locked; that value is unlimited. The default,
+ 64, has generally been sufficient in testing, but you might need to
+ raise this value if you have clients that touch many different
+ tables in a single serializable transaction. This parameter can
+ only be set at server start.
+ </p></dd><dt id="GUC-MAX-PRED-LOCKS-PER-RELATION"><span class="term"><code class="varname">max_pred_locks_per_relation</code> (<code class="type">integer</code>)
+ <a id="id-1.6.7.15.2.4.1.3" class="indexterm"></a>
+ </span></dt><dd><p>
+ This controls how many pages or tuples of a single relation can be
+ predicate-locked before the lock is promoted to covering the whole
+ relation. Values greater than or equal to zero mean an absolute
+ limit, while negative values
+ mean <a class="xref" href="runtime-config-locks.html#GUC-MAX-PRED-LOCKS-PER-TRANSACTION">max_pred_locks_per_transaction</a> divided by
+ the absolute value of this setting. The default is -2, which keeps
+ the behavior from previous versions of <span class="productname">PostgreSQL</span>.
+ This parameter can only be set in the <code class="filename">postgresql.conf</code>
+ file or on the server command line.
+ </p></dd><dt id="GUC-MAX-PRED-LOCKS-PER-PAGE"><span class="term"><code class="varname">max_pred_locks_per_page</code> (<code class="type">integer</code>)
+ <a id="id-1.6.7.15.2.5.1.3" class="indexterm"></a>
+ </span></dt><dd><p>
+ This controls how many rows on a single page can be predicate-locked
+ before the lock is promoted to covering the whole page. The default
+ is 2. This parameter can only be set in
+ the <code class="filename">postgresql.conf</code> file or on the server command line.
+ </p></dd></dl></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="runtime-config-client.html" title="20.11. Client Connection Defaults">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="runtime-config.html" title="Chapter 20. Server Configuration">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="runtime-config-compatible.html" title="20.13. Version and Platform Compatibility">Next</a></td></tr><tr><td width="40%" align="left" valign="top">20.11. Client Connection Defaults </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 20.13. Version and Platform Compatibility</td></tr></table></div></body></html> \ No newline at end of file
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