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1<?xml version="1.0" encoding="UTF-8" standalone="no"?>2<!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>28.2. The Cumulative Statistics System</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="monitoring-ps.html" title="28.1. Standard Unix Tools" /><link rel="next" href="monitoring-locks.html" title="28.3. Viewing Locks" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">28.2. The Cumulative Statistics System</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="monitoring-ps.html" title="28.1. Standard Unix Tools">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="monitoring.html" title="Chapter 28. Monitoring Database Activity">Up</a></td><th width="60%" align="center">Chapter 28. Monitoring Database Activity</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="monitoring-locks.html" title="28.3. Viewing Locks">Next</a></td></tr></table><hr /></div><div class="sect1" id="MONITORING-STATS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">28.2. The Cumulative Statistics System <a href="#MONITORING-STATS" class="id_link">#</a></h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-STATS-SETUP">28.2.1. Statistics Collection Configuration</a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-STATS-VIEWS">28.2.2. Viewing Statistics</a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW">28.2.3. <code class="structname">pg_stat_activity</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-VIEW">28.2.4. <code class="structname">pg_stat_replication</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW">28.2.5. <code class="structname">pg_stat_replication_slots</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-WAL-RECEIVER-VIEW">28.2.6. <code class="structname">pg_stat_wal_receiver</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-RECOVERY-PREFETCH">28.2.7. <code class="structname">pg_stat_recovery_prefetch</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION">28.2.8. <code class="structname">pg_stat_subscription</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION-STATS">28.2.9. <code class="structname">pg_stat_subscription_stats</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-SSL-VIEW">28.2.10. <code class="structname">pg_stat_ssl</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-GSSAPI-VIEW">28.2.11. <code class="structname">pg_stat_gssapi</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-ARCHIVER-VIEW">28.2.12. <code class="structname">pg_stat_archiver</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-IO-VIEW">28.2.13. <code class="structname">pg_stat_io</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-BGWRITER-VIEW">28.2.14. <code class="structname">pg_stat_bgwriter</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW">28.2.15. <code class="structname">pg_stat_wal</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-VIEW">28.2.16. <code class="structname">pg_stat_database</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW">28.2.17. <code class="structname">pg_stat_database_conflicts</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-ALL-TABLES-VIEW">28.2.18. <code class="structname">pg_stat_all_tables</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-ALL-INDEXES-VIEW">28.2.19. <code class="structname">pg_stat_all_indexes</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-TABLES-VIEW">28.2.20. <code class="structname">pg_statio_all_tables</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-INDEXES-VIEW">28.2.21. <code class="structname">pg_statio_all_indexes</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-SEQUENCES-VIEW">28.2.22. <code class="structname">pg_statio_all_sequences</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-USER-FUNCTIONS-VIEW">28.2.23. <code class="structname">pg_stat_user_functions</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-SLRU-VIEW">28.2.24. <code class="structname">pg_stat_slru</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-STATS-FUNCTIONS">28.2.25. Statistics Functions</a></span></dt></dl></div><a id="id-1.6.15.7.2" class="indexterm"></a><p>3 <span class="productname">PostgreSQL</span>'s <em class="firstterm">cumulative statistics4 system</em> supports collection and reporting of information about5 server activity. Presently, accesses to tables and indexes in both6 disk-block and individual-row terms are counted. The total number of rows7 in each table, and information about vacuum and analyze actions for each8 table are also counted. If enabled, calls to user-defined functions and9 the total time spent in each one are counted as well.10 </p><p>11 <span class="productname">PostgreSQL</span> also supports reporting dynamic12 information about exactly what is going on in the system right now, such as13 the exact command currently being executed by other server processes, and14 which other connections exist in the system. This facility is independent15 of the cumulative statistics system.16 </p><div class="sect2" id="MONITORING-STATS-SETUP"><div class="titlepage"><div><div><h3 class="title">28.2.1. Statistics Collection Configuration <a href="#MONITORING-STATS-SETUP" class="id_link">#</a></h3></div></div></div><p>17 Since collection of statistics adds some overhead to query execution,18 the system can be configured to collect or not collect information.19 This is controlled by configuration parameters that are normally set in20 <code class="filename">postgresql.conf</code>. (See <a class="xref" href="runtime-config.html" title="Chapter 20. Server Configuration">Chapter 20</a> for21 details about setting configuration parameters.)22 </p><p>23 The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-ACTIVITIES">track_activities</a> enables monitoring24 of the current command being executed by any server process.25 </p><p>26 The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-COUNTS">track_counts</a> controls whether27 cumulative statistics are collected about table and index accesses.28 </p><p>29 The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-FUNCTIONS">track_functions</a> enables tracking of30 usage of user-defined functions.31 </p><p>32 The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> enables monitoring33 of block read and write times.34 </p><p>35 The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-WAL-IO-TIMING">track_wal_io_timing</a> enables monitoring36 of WAL write times.37 </p><p>38 Normally these parameters are set in <code class="filename">postgresql.conf</code> so39 that they apply to all server processes, but it is possible to turn40 them on or off in individual sessions using the <a class="xref" href="sql-set.html" title="SET"><span class="refentrytitle">SET</span></a> command. (To prevent41 ordinary users from hiding their activity from the administrator,42 only superusers are allowed to change these parameters with43 <code class="command">SET</code>.)44 </p><p>45 Cumulative statistics are collected in shared memory. Every46 <span class="productname">PostgreSQL</span> process collects statistics locally,47 then updates the shared data at appropriate intervals. When a server,48 including a physical replica, shuts down cleanly, a permanent copy of the49 statistics data is stored in the <code class="filename">pg_stat</code> subdirectory,50 so that statistics can be retained across server restarts. In contrast,51 when starting from an unclean shutdown (e.g., after an immediate shutdown,52 a server crash, starting from a base backup, and point-in-time recovery),53 all statistics counters are reset.54 </p></div><div class="sect2" id="MONITORING-STATS-VIEWS"><div class="titlepage"><div><div><h3 class="title">28.2.2. Viewing Statistics <a href="#MONITORING-STATS-VIEWS" class="id_link">#</a></h3></div></div></div><p>55 Several predefined views, listed in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-DYNAMIC-VIEWS-TABLE" title="Table 28.1. Dynamic Statistics Views">Table 28.1</a>, are available to show56 the current state of the system. There are also several other57 views, listed in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-VIEWS-TABLE" title="Table 28.2. Collected Statistics Views">Table 28.2</a>, available to show the accumulated58 statistics. Alternatively, one can59 build custom views using the underlying cumulative statistics functions, as60 discussed in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-FUNCTIONS" title="28.2.25. Statistics Functions">Section 28.2.25</a>.61 </p><p>62 When using the cumulative statistics views and functions to monitor63 collected data, it is important to realize that the information does not64 update instantaneously. Each individual server process flushes out65 accumulated statistics to shared memory just before going idle, but not66 more frequently than once per <code class="varname">PGSTAT_MIN_INTERVAL</code>67 milliseconds (1 second unless altered while building the server); so a68 query or transaction still in progress does not affect the displayed totals69 and the displayed information lags behind actual activity. However,70 current-query information collected by <code class="varname">track_activities</code>71 is always up-to-date.72 </p><p>73 Another important point is that when a server process is asked to display74 any of the accumulated statistics, accessed values are cached until the end75 of its current transaction in the default configuration. So the statistics76 will show static information as long as you continue the current77 transaction. Similarly, information about the current queries of all78 sessions is collected when any such information is first requested within a79 transaction, and the same information will be displayed throughout the80 transaction. This is a feature, not a bug, because it allows you to perform81 several queries on the statistics and correlate the results without82 worrying that the numbers are changing underneath you.83 84 When analyzing statistics interactively, or with expensive queries, the85 time delta between accesses to individual statistics can lead to86 significant skew in the cached statistics. To minimize skew,87 <code class="varname">stats_fetch_consistency</code> can be set to88 <code class="literal">snapshot</code>, at the price of increased memory usage for89 caching not-needed statistics data. Conversely, if it's known that90 statistics are only accessed once, caching accessed statistics is91 unnecessary and can be avoided by setting92 <code class="varname">stats_fetch_consistency</code> to <code class="literal">none</code>.93 94 You can invoke <code class="function">pg_stat_clear_snapshot</code>() to discard the95 current transaction's statistics snapshot or cached values (if any). The96 next use of statistical information will (when in snapshot mode) cause a97 new snapshot to be built or (when in cache mode) accessed statistics to be98 cached.99 </p><p>100 A transaction can also see its own statistics (not yet flushed out to the101 shared memory statistics) in the views102 <code class="structname">pg_stat_xact_all_tables</code>,103 <code class="structname">pg_stat_xact_sys_tables</code>,104 <code class="structname">pg_stat_xact_user_tables</code>, and105 <code class="structname">pg_stat_xact_user_functions</code>. These numbers do not act as106 stated above; instead they update continuously throughout the transaction.107 </p><p>108 Some of the information in the dynamic statistics views shown in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-DYNAMIC-VIEWS-TABLE" title="Table 28.1. Dynamic Statistics Views">Table 28.1</a> is security restricted.109 Ordinary users can only see all the information about their own sessions110 (sessions belonging to a role that they are a member of). In rows about111 other sessions, many columns will be null. Note, however, that the112 existence of a session and its general properties such as its sessions user113 and database are visible to all users. Superusers and roles with privileges of114 built-in role <code class="literal">pg_read_all_stats</code> (see also <a class="xref" href="predefined-roles.html" title="22.5. Predefined Roles">Section 22.5</a>) can see all the information about all sessions.115 </p><div class="table" id="MONITORING-STATS-DYNAMIC-VIEWS-TABLE"><p class="title"><strong>Table 28.1. Dynamic Statistics Views</strong></p><div class="table-contents"><table class="table" summary="Dynamic Statistics Views" border="1"><colgroup><col /><col /></colgroup><thead><tr><th>View Name</th><th>Description</th></tr></thead><tbody><tr><td>116 <code class="structname">pg_stat_activity</code>117 <a id="id-1.6.15.7.6.7.2.2.1.1.2" class="indexterm"></a>118 </td><td>119 One row per server process, showing information related to120 the current activity of that process, such as state and current query.121 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW" title="28.2.3. pg_stat_activity">122 <code class="structname">pg_stat_activity</code></a> for details.123 </td></tr><tr><td><code class="structname">pg_stat_replication</code><a id="id-1.6.15.7.6.7.2.2.2.1.2" class="indexterm"></a></td><td>One row per WAL sender process, showing statistics about124 replication to that sender's connected standby server.125 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-VIEW" title="28.2.4. pg_stat_replication">126 <code class="structname">pg_stat_replication</code></a> for details.127 </td></tr><tr><td><code class="structname">pg_stat_wal_receiver</code><a id="id-1.6.15.7.6.7.2.2.3.1.2" class="indexterm"></a></td><td>Only one row, showing statistics about the WAL receiver from128 that receiver's connected server.129 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-WAL-RECEIVER-VIEW" title="28.2.6. pg_stat_wal_receiver">130 <code class="structname">pg_stat_wal_receiver</code></a> for details.131 </td></tr><tr><td><code class="structname">pg_stat_recovery_prefetch</code><a id="id-1.6.15.7.6.7.2.2.4.1.2" class="indexterm"></a></td><td>Only one row, showing statistics about blocks prefetched during recovery.132 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-RECOVERY-PREFETCH" title="28.2.7. pg_stat_recovery_prefetch">133 <code class="structname">pg_stat_recovery_prefetch</code></a> for details.134 </td></tr><tr><td><code class="structname">pg_stat_subscription</code><a id="id-1.6.15.7.6.7.2.2.5.1.2" class="indexterm"></a></td><td>At least one row per subscription, showing information about135 the subscription workers.136 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION" title="28.2.8. pg_stat_subscription">137 <code class="structname">pg_stat_subscription</code></a> for details.138 </td></tr><tr><td><code class="structname">pg_stat_ssl</code><a id="id-1.6.15.7.6.7.2.2.6.1.2" class="indexterm"></a></td><td>One row per connection (regular and replication), showing information about139 SSL used on this connection.140 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SSL-VIEW" title="28.2.10. pg_stat_ssl">141 <code class="structname">pg_stat_ssl</code></a> for details.142 </td></tr><tr><td><code class="structname">pg_stat_gssapi</code><a id="id-1.6.15.7.6.7.2.2.7.1.2" class="indexterm"></a></td><td>One row per connection (regular and replication), showing information about143 GSSAPI authentication and encryption used on this connection.144 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-GSSAPI-VIEW" title="28.2.11. pg_stat_gssapi">145 <code class="structname">pg_stat_gssapi</code></a> for details.146 </td></tr><tr><td><code class="structname">pg_stat_progress_analyze</code><a id="id-1.6.15.7.6.7.2.2.8.1.2" class="indexterm"></a></td><td>One row for each backend (including autovacuum worker processes) running147 <code class="command">ANALYZE</code>, showing current progress.148 See <a class="xref" href="progress-reporting.html#ANALYZE-PROGRESS-REPORTING" title="28.4.1. ANALYZE Progress Reporting">Section 28.4.1</a>.149 </td></tr><tr><td><code class="structname">pg_stat_progress_create_index</code><a id="id-1.6.15.7.6.7.2.2.9.1.2" class="indexterm"></a></td><td>One row for each backend running <code class="command">CREATE INDEX</code> or <code class="command">REINDEX</code>, showing150 current progress.151 See <a class="xref" href="progress-reporting.html#CREATE-INDEX-PROGRESS-REPORTING" title="28.4.4. CREATE INDEX Progress Reporting">Section 28.4.4</a>.152 </td></tr><tr><td><code class="structname">pg_stat_progress_vacuum</code><a id="id-1.6.15.7.6.7.2.2.10.1.2" class="indexterm"></a></td><td>One row for each backend (including autovacuum worker processes) running153 <code class="command">VACUUM</code>, showing current progress.154 See <a class="xref" href="progress-reporting.html#VACUUM-PROGRESS-REPORTING" title="28.4.5. VACUUM Progress Reporting">Section 28.4.5</a>.155 </td></tr><tr><td><code class="structname">pg_stat_progress_cluster</code><a id="id-1.6.15.7.6.7.2.2.11.1.2" class="indexterm"></a></td><td>One row for each backend running156 <code class="command">CLUSTER</code> or <code class="command">VACUUM FULL</code>, showing current progress.157 See <a class="xref" href="progress-reporting.html#CLUSTER-PROGRESS-REPORTING" title="28.4.2. CLUSTER Progress Reporting">Section 28.4.2</a>.158 </td></tr><tr><td><code class="structname">pg_stat_progress_basebackup</code><a id="id-1.6.15.7.6.7.2.2.12.1.2" class="indexterm"></a></td><td>One row for each WAL sender process streaming a base backup,159 showing current progress.160 See <a class="xref" href="progress-reporting.html#BASEBACKUP-PROGRESS-REPORTING" title="28.4.6. Base Backup Progress Reporting">Section 28.4.6</a>.161 </td></tr><tr><td><code class="structname">pg_stat_progress_copy</code><a id="id-1.6.15.7.6.7.2.2.13.1.2" class="indexterm"></a></td><td>One row for each backend running <code class="command">COPY</code>, showing current progress.162 See <a class="xref" href="progress-reporting.html#COPY-PROGRESS-REPORTING" title="28.4.3. COPY Progress Reporting">Section 28.4.3</a>.163 </td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="MONITORING-STATS-VIEWS-TABLE"><p class="title"><strong>Table 28.2. Collected Statistics Views</strong></p><div class="table-contents"><table class="table" summary="Collected Statistics Views" border="1"><colgroup><col /><col /></colgroup><thead><tr><th>View Name</th><th>Description</th></tr></thead><tbody><tr><td><code class="structname">pg_stat_archiver</code><a id="id-1.6.15.7.6.8.2.2.1.1.2" class="indexterm"></a></td><td>One row only, showing statistics about the164 WAL archiver process's activity. See165 <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ARCHIVER-VIEW" title="28.2.12. pg_stat_archiver">166 <code class="structname">pg_stat_archiver</code></a> for details.167 </td></tr><tr><td><code class="structname">pg_stat_bgwriter</code><a id="id-1.6.15.7.6.8.2.2.2.1.2" class="indexterm"></a></td><td>One row only, showing statistics about the168 background writer process's activity. See169 <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-BGWRITER-VIEW" title="28.2.14. pg_stat_bgwriter">170 <code class="structname">pg_stat_bgwriter</code></a> for details.171 </td></tr><tr><td><code class="structname">pg_stat_database</code><a id="id-1.6.15.7.6.8.2.2.3.1.2" class="indexterm"></a></td><td>One row per database, showing database-wide statistics. See172 <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-VIEW" title="28.2.16. pg_stat_database">173 <code class="structname">pg_stat_database</code></a> for details.174 </td></tr><tr><td><code class="structname">pg_stat_database_conflicts</code><a id="id-1.6.15.7.6.8.2.2.4.1.2" class="indexterm"></a></td><td>175 One row per database, showing database-wide statistics about176 query cancels due to conflict with recovery on standby servers.177 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW" title="28.2.17. pg_stat_database_conflicts">178 <code class="structname">pg_stat_database_conflicts</code></a> for details.179 </td></tr><tr><td><code class="structname">pg_stat_io</code><a id="id-1.6.15.7.6.8.2.2.5.1.2" class="indexterm"></a></td><td>180 One row for each combination of backend type, context, and target object181 containing cluster-wide I/O statistics.182 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-IO-VIEW" title="28.2.13. pg_stat_io">183 <code class="structname">pg_stat_io</code></a> for details.184 </td></tr><tr><td><code class="structname">pg_stat_replication_slots</code><a id="id-1.6.15.7.6.8.2.2.6.1.2" class="indexterm"></a></td><td>One row per replication slot, showing statistics about the185 replication slot's usage. See186 <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW" title="28.2.5. pg_stat_replication_slots">187 <code class="structname">pg_stat_replication_slots</code></a> for details.188 </td></tr><tr><td><code class="structname">pg_stat_slru</code><a id="id-1.6.15.7.6.8.2.2.7.1.2" class="indexterm"></a></td><td>One row per SLRU, showing statistics of operations. See189 <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SLRU-VIEW" title="28.2.24. pg_stat_slru">190 <code class="structname">pg_stat_slru</code></a> for details.191 </td></tr><tr><td><code class="structname">pg_stat_subscription_stats</code><a id="id-1.6.15.7.6.8.2.2.8.1.2" class="indexterm"></a></td><td>One row per subscription, showing statistics about errors.192 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION-STATS" title="28.2.9. pg_stat_subscription_stats">193 <code class="structname">pg_stat_subscription_stats</code></a> for details.194 </td></tr><tr><td><code class="structname">pg_stat_wal</code><a id="id-1.6.15.7.6.8.2.2.9.1.2" class="indexterm"></a></td><td>One row only, showing statistics about WAL activity. See195 <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW" title="28.2.15. pg_stat_wal">196 <code class="structname">pg_stat_wal</code></a> for details.197 </td></tr><tr><td><code class="structname">pg_stat_all_tables</code><a id="id-1.6.15.7.6.8.2.2.10.1.2" class="indexterm"></a></td><td>198 One row for each table in the current database, showing statistics199 about accesses to that specific table.200 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ALL-TABLES-VIEW" title="28.2.18. pg_stat_all_tables">201 <code class="structname">pg_stat_all_tables</code></a> for details.202 </td></tr><tr><td><code class="structname">pg_stat_sys_tables</code><a id="id-1.6.15.7.6.8.2.2.11.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_tables</code>, except that only203 system tables are shown.</td></tr><tr><td><code class="structname">pg_stat_user_tables</code><a id="id-1.6.15.7.6.8.2.2.12.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_tables</code>, except that only user204 tables are shown.</td></tr><tr><td><code class="structname">pg_stat_xact_all_tables</code><a id="id-1.6.15.7.6.8.2.2.13.1.2" class="indexterm"></a></td><td>Similar to <code class="structname">pg_stat_all_tables</code>, but counts actions205 taken so far within the current transaction (which are <span class="emphasis"><em>not</em></span>206 yet included in <code class="structname">pg_stat_all_tables</code> and related views).207 The columns for numbers of live and dead rows and vacuum and208 analyze actions are not present in this view.</td></tr><tr><td><code class="structname">pg_stat_xact_sys_tables</code><a id="id-1.6.15.7.6.8.2.2.14.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_xact_all_tables</code>, except that only209 system tables are shown.</td></tr><tr><td><code class="structname">pg_stat_xact_user_tables</code><a id="id-1.6.15.7.6.8.2.2.15.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_xact_all_tables</code>, except that only210 user tables are shown.</td></tr><tr><td><code class="structname">pg_stat_all_indexes</code><a id="id-1.6.15.7.6.8.2.2.16.1.2" class="indexterm"></a></td><td>211 One row for each index in the current database, showing statistics212 about accesses to that specific index.213 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ALL-INDEXES-VIEW" title="28.2.19. pg_stat_all_indexes">214 <code class="structname">pg_stat_all_indexes</code></a> for details.215 </td></tr><tr><td><code class="structname">pg_stat_sys_indexes</code><a id="id-1.6.15.7.6.8.2.2.17.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_indexes</code>, except that only216 indexes on system tables are shown.</td></tr><tr><td><code class="structname">pg_stat_user_indexes</code><a id="id-1.6.15.7.6.8.2.2.18.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_indexes</code>, except that only217 indexes on user tables are shown.</td></tr><tr><td><code class="structname">pg_stat_user_functions</code><a id="id-1.6.15.7.6.8.2.2.19.1.2" class="indexterm"></a></td><td>218 One row for each tracked function, showing statistics219 about executions of that function. See220 <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-USER-FUNCTIONS-VIEW" title="28.2.23. pg_stat_user_functions">221 <code class="structname">pg_stat_user_functions</code></a> for details.222 </td></tr><tr><td><code class="structname">pg_stat_xact_user_functions</code><a id="id-1.6.15.7.6.8.2.2.20.1.2" class="indexterm"></a></td><td>Similar to <code class="structname">pg_stat_user_functions</code>, but counts only223 calls during the current transaction (which are <span class="emphasis"><em>not</em></span>224 yet included in <code class="structname">pg_stat_user_functions</code>).</td></tr><tr><td><code class="structname">pg_statio_all_tables</code><a id="id-1.6.15.7.6.8.2.2.21.1.2" class="indexterm"></a></td><td>225 One row for each table in the current database, showing statistics226 about I/O on that specific table.227 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-TABLES-VIEW" title="28.2.20. pg_statio_all_tables">228 <code class="structname">pg_statio_all_tables</code></a> for details.229 </td></tr><tr><td><code class="structname">pg_statio_sys_tables</code><a id="id-1.6.15.7.6.8.2.2.22.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_tables</code>, except that only230 system tables are shown.</td></tr><tr><td><code class="structname">pg_statio_user_tables</code><a id="id-1.6.15.7.6.8.2.2.23.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_tables</code>, except that only231 user tables are shown.</td></tr><tr><td><code class="structname">pg_statio_all_indexes</code><a id="id-1.6.15.7.6.8.2.2.24.1.2" class="indexterm"></a></td><td>232 One row for each index in the current database,233 showing statistics about I/O on that specific index.234 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-INDEXES-VIEW" title="28.2.21. pg_statio_all_indexes">235 <code class="structname">pg_statio_all_indexes</code></a> for details.236 </td></tr><tr><td><code class="structname">pg_statio_sys_indexes</code><a id="id-1.6.15.7.6.8.2.2.25.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_indexes</code>, except that only237 indexes on system tables are shown.</td></tr><tr><td><code class="structname">pg_statio_user_indexes</code><a id="id-1.6.15.7.6.8.2.2.26.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_indexes</code>, except that only238 indexes on user tables are shown.</td></tr><tr><td><code class="structname">pg_statio_all_sequences</code><a id="id-1.6.15.7.6.8.2.2.27.1.2" class="indexterm"></a></td><td>239 One row for each sequence in the current database,240 showing statistics about I/O on that specific sequence.241 See <a class="link" href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-SEQUENCES-VIEW" title="28.2.22. pg_statio_all_sequences">242 <code class="structname">pg_statio_all_sequences</code></a> for details.243 </td></tr><tr><td><code class="structname">pg_statio_sys_sequences</code><a id="id-1.6.15.7.6.8.2.2.28.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_sequences</code>, except that only244 system sequences are shown. (Presently, no system sequences are defined,245 so this view is always empty.)</td></tr><tr><td><code class="structname">pg_statio_user_sequences</code><a id="id-1.6.15.7.6.8.2.2.29.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_sequences</code>, except that only246 user sequences are shown.</td></tr></tbody></table></div></div><br class="table-break" /><p>247 The per-index statistics are particularly useful to determine which248 indexes are being used and how effective they are.249 </p><p>250 The <code class="structname">pg_stat_io</code> and251 <code class="structname">pg_statio_</code> set of views are useful for determining252 the effectiveness of the buffer cache. They can be used to calculate a cache253 hit ratio. Note that while <span class="productname">PostgreSQL</span>'s I/O254 statistics capture most instances in which the kernel was invoked in order255 to perform I/O, they do not differentiate between data which had to be256 fetched from disk and that which already resided in the kernel page cache.257 Users are advised to use the <span class="productname">PostgreSQL</span>258 statistics views in combination with operating system utilities for a more259 complete picture of their database's I/O performance.260 </p></div><div class="sect2" id="MONITORING-PG-STAT-ACTIVITY-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.3. <code class="structname">pg_stat_activity</code> <a href="#MONITORING-PG-STAT-ACTIVITY-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.15.7.7.2" class="indexterm"></a><p>261 The <code class="structname">pg_stat_activity</code> view will have one row262 per server process, showing information related to263 the current activity of that process.264 </p><div class="table" id="PG-STAT-ACTIVITY-VIEW"><p class="title"><strong>Table 28.3. <code class="structname">pg_stat_activity</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_activity View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">265 Column Type266 </p>267 <p>268 Description269 </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">270 <code class="structfield">datid</code> <code class="type">oid</code>271 </p>272 <p>273 OID of the database this backend is connected to274 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">275 <code class="structfield">datname</code> <code class="type">name</code>276 </p>277 <p>278 Name of the database this backend is connected to279 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">280 <code class="structfield">pid</code> <code class="type">integer</code>281 </p>282 <p>283 Process ID of this backend284 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">285 <code class="structfield">leader_pid</code> <code class="type">integer</code>286 </p>287 <p>288 Process ID of the parallel group leader if this process is a parallel289 query worker, or process ID of the leader apply worker if this process290 is a parallel apply worker. <code class="literal">NULL</code> indicates that this291 process is a parallel group leader or leader apply worker, or does not292 participate in any parallel operation.293 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">294 <code class="structfield">usesysid</code> <code class="type">oid</code>295 </p>296 <p>297 OID of the user logged into this backend298 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">299 <code class="structfield">usename</code> <code class="type">name</code>300 </p>301 <p>302 Name of the user logged into this backend303 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">304 <code class="structfield">application_name</code> <code class="type">text</code>305 </p>306 <p>307 Name of the application that is connected308 to this backend309 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">310 <code class="structfield">client_addr</code> <code class="type">inet</code>311 </p>312 <p>313 IP address of the client connected to this backend.314 If this field is null, it indicates either that the client is315 connected via a Unix socket on the server machine or that this is an316 internal process such as autovacuum.317 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">318 <code class="structfield">client_hostname</code> <code class="type">text</code>319 </p>320 <p>321 Host name of the connected client, as reported by a322 reverse DNS lookup of <code class="structfield">client_addr</code>. This field will323 only be non-null for IP connections, and only when <a class="xref" href="runtime-config-logging.html#GUC-LOG-HOSTNAME">log_hostname</a> is enabled.324 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">325 <code class="structfield">client_port</code> <code class="type">integer</code>326 </p>327 <p>328 TCP port number that the client is using for communication329 with this backend, or <code class="literal">-1</code> if a Unix socket is used.330 If this field is null, it indicates that this is an internal server process.331 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">332 <code class="structfield">backend_start</code> <code class="type">timestamp with time zone</code>333 </p>334 <p>335 Time when this process was started. For client backends,336 this is the time the client connected to the server.337 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">338 <code class="structfield">xact_start</code> <code class="type">timestamp with time zone</code>339 </p>340 <p>341 Time when this process' current transaction was started, or null342 if no transaction is active. If the current343 query is the first of its transaction, this column is equal to the344 <code class="structfield">query_start</code> column.345 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">346 <code class="structfield">query_start</code> <code class="type">timestamp with time zone</code>347 </p>348 <p>349 Time when the currently active query was started, or if350 <code class="structfield">state</code> is not <code class="literal">active</code>, when the last query351 was started352 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">353 <code class="structfield">state_change</code> <code class="type">timestamp with time zone</code>354 </p>355 <p>356 Time when the <code class="structfield">state</code> was last changed357 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">358 <code class="structfield">wait_event_type</code> <code class="type">text</code>359 </p>360 <p>361 The type of event for which the backend is waiting, if any;362 otherwise NULL. See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TABLE" title="Table 28.4. Wait Event Types">Table 28.4</a>.363 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">364 <code class="structfield">wait_event</code> <code class="type">text</code>365 </p>366 <p>367 Wait event name if backend is currently waiting, otherwise NULL.368 See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-ACTIVITY-TABLE" title="Table 28.5. Wait Events of Type Activity">Table 28.5</a> through369 <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TIMEOUT-TABLE" title="Table 28.13. Wait Events of Type Timeout">Table 28.13</a>.370 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">371 <code class="structfield">state</code> <code class="type">text</code>372 </p>373 <p>374 Current overall state of this backend.375 Possible values are:376 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>377 <code class="literal">active</code>: The backend is executing a query.378 </p></li><li class="listitem"><p>379 <code class="literal">idle</code>: The backend is waiting for a new client command.380 </p></li><li class="listitem"><p>381 <code class="literal">idle in transaction</code>: The backend is in a transaction,382 but is not currently executing a query.383 </p></li><li class="listitem"><p>384 <code class="literal">idle in transaction (aborted)</code>: This state is similar to385 <code class="literal">idle in transaction</code>, except one of the statements in386 the transaction caused an error.387 </p></li><li class="listitem"><p>388 <code class="literal">fastpath function call</code>: The backend is executing a389 fast-path function.390 </p></li><li class="listitem"><p>391 <code class="literal">disabled</code>: This state is reported if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-ACTIVITIES">track_activities</a> is disabled in this backend.392 </p></li></ul></div><p>393 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">394 <code class="structfield">backend_xid</code> <code class="type">xid</code>395 </p>396 <p>397 Top-level transaction identifier of this backend, if any; see398 <a class="xref" href="transaction-id.html" title="74.1. Transactions and Identifiers">Section 74.1</a>.399 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">400 <code class="structfield">backend_xmin</code> <code class="type">xid</code>401 </p>402 <p>403 The current backend's <code class="literal">xmin</code> horizon.404 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">405 <code class="structfield">query_id</code> <code class="type">bigint</code>406 </p>407 <p>408 Identifier of this backend's most recent query. If409 <code class="structfield">state</code> is <code class="literal">active</code> this410 field shows the identifier of the currently executing query. In411 all other states, it shows the identifier of last query that was412 executed. Query identifiers are not computed by default so this413 field will be null unless <a class="xref" href="runtime-config-statistics.html#GUC-COMPUTE-QUERY-ID">compute_query_id</a>414 parameter is enabled or a third-party module that computes query415 identifiers is configured.416 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">417 <code class="structfield">query</code> <code class="type">text</code>418 </p>419 <p>420 Text of this backend's most recent query. If421 <code class="structfield">state</code> is <code class="literal">active</code> this field shows the422 currently executing query. In all other states, it shows the last query423 that was executed. By default the query text is truncated at 1024424 bytes; this value can be changed via the parameter425 <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-ACTIVITY-QUERY-SIZE">track_activity_query_size</a>.426 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">427 <code class="structfield">backend_type</code> <code class="type">text</code>428 </p>429 <p>430 Type of current backend. Possible types are431 <code class="literal">autovacuum launcher</code>, <code class="literal">autovacuum worker</code>,432 <code class="literal">logical replication launcher</code>,433 <code class="literal">logical replication worker</code>,434 <code class="literal">parallel worker</code>, <code class="literal">background writer</code>,435 <code class="literal">client backend</code>, <code class="literal">checkpointer</code>,436 <code class="literal">archiver</code>, <code class="literal">standalone backend</code>,437 <code class="literal">startup</code>, <code class="literal">walreceiver</code>,438 <code class="literal">walsender</code> and <code class="literal">walwriter</code>.439 In addition, background workers registered by extensions may have440 additional types.441 </p></td></tr></tbody></table></div></div><br class="table-break" /><div class="note"><h3 class="title">Note</h3><p>442 The <code class="structfield">wait_event</code> and <code class="structfield">state</code> columns are443 independent. If a backend is in the <code class="literal">active</code> state,444 it may or may not be <code class="literal">waiting</code> on some event. If the state445 is <code class="literal">active</code> and <code class="structfield">wait_event</code> is non-null, it446 means that a query is being executed, but is being blocked somewhere447 in the system.448 </p></div><div class="table" id="WAIT-EVENT-TABLE"><p class="title"><strong>Table 28.4. Wait Event Types</strong></p><div class="table-contents"><table class="table" summary="Wait Event Types" border="1"><colgroup><col /><col /></colgroup><thead><tr><th>Wait Event Type</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">Activity</code></td><td>The server process is idle. This event type indicates a process449 waiting for activity in its main processing loop.450 <code class="literal">wait_event</code> will identify the specific wait point;451 see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-ACTIVITY-TABLE" title="Table 28.5. Wait Events of Type Activity">Table 28.5</a>.452 </td></tr><tr><td><code class="literal">BufferPin</code></td><td>The server process is waiting for exclusive access to453 a data buffer. Buffer pin waits can be protracted if454 another process holds an open cursor that last read data from the455 buffer in question. See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-BUFFERPIN-TABLE" title="Table 28.6. Wait Events of Type BufferPin">Table 28.6</a>.456 </td></tr><tr><td><code class="literal">Client</code></td><td>The server process is waiting for activity on a socket457 connected to a user application. Thus, the server expects something458 to happen that is independent of its internal processes.459 <code class="literal">wait_event</code> will identify the specific wait point;460 see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-CLIENT-TABLE" title="Table 28.7. Wait Events of Type Client">Table 28.7</a>.461 </td></tr><tr><td><code class="literal">Extension</code></td><td>The server process is waiting for some condition defined by an462 extension module.463 See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-EXTENSION-TABLE" title="Table 28.8. Wait Events of Type Extension">Table 28.8</a>.464 </td></tr><tr><td><code class="literal">IO</code></td><td>The server process is waiting for an I/O operation to complete.465 <code class="literal">wait_event</code> will identify the specific wait point;466 see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-IO-TABLE" title="Table 28.9. Wait Events of Type IO">Table 28.9</a>.467 </td></tr><tr><td><code class="literal">IPC</code></td><td>The server process is waiting for some interaction with468 another server process. <code class="literal">wait_event</code> will469 identify the specific wait point;470 see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-IPC-TABLE" title="Table 28.10. Wait Events of Type IPC">Table 28.10</a>.471 </td></tr><tr><td><code class="literal">Lock</code></td><td>The server process is waiting for a heavyweight lock.472 Heavyweight locks, also known as lock manager locks or simply locks,473 primarily protect SQL-visible objects such as tables. However,474 they are also used to ensure mutual exclusion for certain internal475 operations such as relation extension. <code class="literal">wait_event</code>476 will identify the type of lock awaited;477 see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-LOCK-TABLE" title="Table 28.11. Wait Events of Type Lock">Table 28.11</a>.478 </td></tr><tr><td><code class="literal">LWLock</code></td><td> The server process is waiting for a lightweight lock.479 Most such locks protect a particular data structure in shared memory.480 <code class="literal">wait_event</code> will contain a name identifying the purpose481 of the lightweight lock. (Some locks have specific names; others482 are part of a group of locks each with a similar purpose.)483 See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-LWLOCK-TABLE" title="Table 28.12. Wait Events of Type LWLock">Table 28.12</a>.484 </td></tr><tr><td><code class="literal">Timeout</code></td><td>The server process is waiting for a timeout485 to expire. <code class="literal">wait_event</code> will identify the specific wait486 point; see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TIMEOUT-TABLE" title="Table 28.13. Wait Events of Type Timeout">Table 28.13</a>.487 </td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="WAIT-EVENT-ACTIVITY-TABLE"><p class="title"><strong>Table 28.5. Wait Events of Type <code class="literal">Activity</code></strong></p><div class="table-contents"><table class="table" summary="Wait Events of Type Activity" border="1"><colgroup><col /><col /></colgroup><thead><tr><th><code class="literal">Activity</code> Wait Event</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">ArchiverMain</code></td><td>Waiting in main loop of archiver process.</td></tr><tr><td><code class="literal">AutoVacuumMain</code></td><td>Waiting in main loop of autovacuum launcher process.</td></tr><tr><td><code class="literal">BgWriterHibernate</code></td><td>Waiting in background writer process, hibernating.</td></tr><tr><td><code class="literal">BgWriterMain</code></td><td>Waiting in main loop of background writer process.</td></tr><tr><td><code class="literal">CheckpointerMain</code></td><td>Waiting in main loop of checkpointer process.</td></tr><tr><td><code class="literal">LogicalApplyMain</code></td><td>Waiting in main loop of logical replication apply process.</td></tr><tr><td><code class="literal">LogicalLauncherMain</code></td><td>Waiting in main loop of logical replication launcher process.</td></tr><tr><td><code class="literal">LogicalParallelApplyMain</code></td><td>Waiting in main loop of logical replication parallel apply488 process.</td></tr><tr><td><code class="literal">RecoveryWalStream</code></td><td>Waiting in main loop of startup process for WAL to arrive, during489 streaming recovery.</td></tr><tr><td><code class="literal">SysLoggerMain</code></td><td>Waiting in main loop of syslogger process.</td></tr><tr><td><code class="literal">WalReceiverMain</code></td><td>Waiting in main loop of WAL receiver process.</td></tr><tr><td><code class="literal">WalSenderMain</code></td><td>Waiting in main loop of WAL sender process.</td></tr><tr><td><code class="literal">WalWriterMain</code></td><td>Waiting in main loop of WAL writer process.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="WAIT-EVENT-BUFFERPIN-TABLE"><p class="title"><strong>Table 28.6. Wait Events of Type <code class="literal">BufferPin</code></strong></p><div class="table-contents"><table class="table" summary="Wait Events of Type BufferPin" border="1"><colgroup><col /><col /></colgroup><thead><tr><th><code class="literal">BufferPin</code> Wait Event</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">BufferPin</code></td><td>Waiting to acquire an exclusive pin on a buffer.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="WAIT-EVENT-CLIENT-TABLE"><p class="title"><strong>Table 28.7. Wait Events of Type <code class="literal">Client</code></strong></p><div class="table-contents"><table class="table" summary="Wait Events of Type Client" border="1"><colgroup><col /><col /></colgroup><thead><tr><th><code class="literal">Client</code> Wait Event</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">ClientRead</code></td><td>Waiting to read data from the client.</td></tr><tr><td><code class="literal">ClientWrite</code></td><td>Waiting to write data to the client.</td></tr><tr><td><code class="literal">GSSOpenServer</code></td><td>Waiting to read data from the client while establishing a GSSAPI490 session.</td></tr><tr><td><code class="literal">LibPQWalReceiverConnect</code></td><td>Waiting in WAL receiver to establish connection to remote491 server.</td></tr><tr><td><code class="literal">LibPQWalReceiverReceive</code></td><td>Waiting in WAL receiver to receive data from remote server.</td></tr><tr><td><code class="literal">SSLOpenServer</code></td><td>Waiting for SSL while attempting connection.</td></tr><tr><td><code class="literal">WalSenderWaitForWAL</code></td><td>Waiting for WAL to be flushed in WAL sender process.</td></tr><tr><td><code class="literal">WalSenderWriteData</code></td><td>Waiting for any activity when processing replies from WAL492 receiver in WAL sender process.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="WAIT-EVENT-EXTENSION-TABLE"><p class="title"><strong>Table 28.8. Wait Events of Type <code class="literal">Extension</code></strong></p><div class="table-contents"><table class="table" summary="Wait Events of Type Extension" border="1"><colgroup><col /><col /></colgroup><thead><tr><th><code class="literal">Extension</code> Wait Event</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">Extension</code></td><td>Waiting in an extension.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="WAIT-EVENT-IO-TABLE"><p class="title"><strong>Table 28.9. Wait Events of Type <code class="literal">IO</code></strong></p><div class="table-contents"><table class="table" summary="Wait Events of Type IO" border="1"><colgroup><col /><col /></colgroup><thead><tr><th><code class="literal">IO</code> Wait Event</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">BaseBackupRead</code></td><td>Waiting for base backup to read from a file.</td></tr><tr><td><code class="literal">BaseBackupSync</code></td><td>Waiting for data written by a base backup to reach durable storage.</td></tr><tr><td><code class="literal">BaseBackupWrite</code></td><td>Waiting for base backup to write to a file.</td></tr><tr><td><code class="literal">BufFileRead</code></td><td>Waiting for a read from a buffered file.</td></tr><tr><td><code class="literal">BufFileTruncate</code></td><td>Waiting for a buffered file to be truncated.</td></tr><tr><td><code class="literal">BufFileWrite</code></td><td>Waiting for a write to a buffered file.</td></tr><tr><td><code class="literal">ControlFileRead</code></td><td>Waiting for a read from the <code class="filename">pg_control</code>493 file.</td></tr><tr><td><code class="literal">ControlFileSync</code></td><td>Waiting for the <code class="filename">pg_control</code> file to reach494 durable storage.</td></tr><tr><td><code class="literal">ControlFileSyncUpdate</code></td><td>Waiting for an update to the <code class="filename">pg_control</code> file495 to reach durable storage.</td></tr><tr><td><code class="literal">ControlFileWrite</code></td><td>Waiting for a write to the <code class="filename">pg_control</code>496 file.</td></tr><tr><td><code class="literal">ControlFileWriteUpdate</code></td><td>Waiting for a write to update the <code class="filename">pg_control</code>497 file.</td></tr><tr><td><code class="literal">CopyFileRead</code></td><td>Waiting for a read during a file copy operation.</td></tr><tr><td><code class="literal">CopyFileWrite</code></td><td>Waiting for a write during a file copy operation.</td></tr><tr><td><code class="literal">DSMAllocate</code></td><td>Waiting for a dynamic shared memory segment to be498 allocated.</td></tr><tr><td><code class="literal">DSMFillZeroWrite</code></td><td>Waiting to fill a dynamic shared memory backing file with499 zeroes.</td></tr><tr><td><code class="literal">DataFileExtend</code></td><td>Waiting for a relation data file to be extended.</td></tr><tr><td><code class="literal">DataFileFlush</code></td><td>Waiting for a relation data file to reach durable storage.</td></tr><tr><td><code class="literal">DataFileImmediateSync</code></td><td>Waiting for an immediate synchronization of a relation data file to500 durable storage.</td></tr><tr><td><code class="literal">DataFilePrefetch</code></td><td>Waiting for an asynchronous prefetch from a relation data501 file.</td></tr><tr><td><code class="literal">DataFileRead</code></td><td>Waiting for a read from a relation data file.</td></tr><tr><td><code class="literal">DataFileSync</code></td><td>Waiting for changes to a relation data file to reach durable storage.</td></tr><tr><td><code class="literal">DataFileTruncate</code></td><td>Waiting for a relation data file to be truncated.</td></tr><tr><td><code class="literal">DataFileWrite</code></td><td>Waiting for a write to a relation data file.</td></tr><tr><td><code class="literal">LockFileAddToDataDirRead</code></td><td>Waiting for a read while adding a line to the data directory lock502 file.</td></tr><tr><td><code class="literal">LockFileAddToDataDirSync</code></td><td>Waiting for data to reach durable storage while adding a line to the503 data directory lock file.</td></tr><tr><td><code class="literal">LockFileAddToDataDirWrite</code></td><td>Waiting for a write while adding a line to the data directory504 lock file.</td></tr><tr><td><code class="literal">LockFileCreateRead</code></td><td>Waiting to read while creating the data directory lock505 file.</td></tr><tr><td><code class="literal">LockFileCreateSync</code></td><td>Waiting for data to reach durable storage while creating the data506 directory lock file.</td></tr><tr><td><code class="literal">LockFileCreateWrite</code></td><td>Waiting for a write while creating the data directory lock507 file.</td></tr><tr><td><code class="literal">LockFileReCheckDataDirRead</code></td><td>Waiting for a read during recheck of the data directory lock508 file.</td></tr><tr><td><code class="literal">LogicalRewriteCheckpointSync</code></td><td>Waiting for logical rewrite mappings to reach durable storage509 during a checkpoint.</td></tr><tr><td><code class="literal">LogicalRewriteMappingSync</code></td><td>Waiting for mapping data to reach durable storage during a logical510 rewrite.</td></tr><tr><td><code class="literal">LogicalRewriteMappingWrite</code></td><td>Waiting for a write of mapping data during a logical511 rewrite.</td></tr><tr><td><code class="literal">LogicalRewriteSync</code></td><td>Waiting for logical rewrite mappings to reach durable512 storage.</td></tr><tr><td><code class="literal">LogicalRewriteTruncate</code></td><td>Waiting for truncate of mapping data during a logical513 rewrite.</td></tr><tr><td><code class="literal">LogicalRewriteWrite</code></td><td>Waiting for a write of logical rewrite mappings.</td></tr><tr><td><code class="literal">RelationMapRead</code></td><td>Waiting for a read of the relation map file.</td></tr><tr><td><code class="literal">RelationMapReplace</code></td><td>Waiting for durable replacement of a relation map file.</td></tr><tr><td><code class="literal">RelationMapWrite</code></td><td>Waiting for a write to the relation map file.</td></tr><tr><td><code class="literal">ReorderBufferRead</code></td><td>Waiting for a read during reorder buffer management.</td></tr><tr><td><code class="literal">ReorderBufferWrite</code></td><td>Waiting for a write during reorder buffer management.</td></tr><tr><td><code class="literal">ReorderLogicalMappingRead</code></td><td>Waiting for a read of a logical mapping during reorder buffer514 management.</td></tr><tr><td><code class="literal">ReplicationSlotRead</code></td><td>Waiting for a read from a replication slot control file.</td></tr><tr><td><code class="literal">ReplicationSlotRestoreSync</code></td><td>Waiting for a replication slot control file to reach durable storage515 while restoring it to memory.</td></tr><tr><td><code class="literal">ReplicationSlotSync</code></td><td>Waiting for a replication slot control file to reach durable516 storage.</td></tr><tr><td><code class="literal">ReplicationSlotWrite</code></td><td>Waiting for a write to a replication slot control file.</td></tr><tr><td><code class="literal">SLRUFlushSync</code></td><td>Waiting for SLRU data to reach durable storage during a checkpoint517 or database shutdown.</td></tr><tr><td><code class="literal">SLRURead</code></td><td>Waiting for a read of an SLRU page.</td></tr><tr><td><code class="literal">SLRUSync</code></td><td>Waiting for SLRU data to reach durable storage following a page518 write.</td></tr><tr><td><code class="literal">SLRUWrite</code></td><td>Waiting for a write of an SLRU page.</td></tr><tr><td><code class="literal">SnapbuildRead</code></td><td>Waiting for a read of a serialized historical catalog519 snapshot.</td></tr><tr><td><code class="literal">SnapbuildSync</code></td><td>Waiting for a serialized historical catalog snapshot to reach520 durable storage.</td></tr><tr><td><code class="literal">SnapbuildWrite</code></td><td>Waiting for a write of a serialized historical catalog521 snapshot.</td></tr><tr><td><code class="literal">TimelineHistoryFileSync</code></td><td>Waiting for a timeline history file received via streaming522 replication to reach durable storage.</td></tr><tr><td><code class="literal">TimelineHistoryFileWrite</code></td><td>Waiting for a write of a timeline history file received via523 streaming replication.</td></tr><tr><td><code class="literal">TimelineHistoryRead</code></td><td>Waiting for a read of a timeline history file.</td></tr><tr><td><code class="literal">TimelineHistorySync</code></td><td>Waiting for a newly created timeline history file to reach durable524 storage.</td></tr><tr><td><code class="literal">TimelineHistoryWrite</code></td><td>Waiting for a write of a newly created timeline history525 file.</td></tr><tr><td><code class="literal">TwophaseFileRead</code></td><td>Waiting for a read of a two phase state file.</td></tr><tr><td><code class="literal">TwophaseFileSync</code></td><td>Waiting for a two phase state file to reach durable storage.</td></tr><tr><td><code class="literal">TwophaseFileWrite</code></td><td>Waiting for a write of a two phase state file.</td></tr><tr><td><code class="literal">VersionFileSync</code></td><td>Waiting for the version file to reach durable storage while526 creating a database.</td></tr><tr><td><code class="literal">VersionFileWrite</code></td><td>Waiting for the version file to be written while creating a database.</td></tr><tr><td><code class="literal">WALBootstrapSync</code></td><td>Waiting for WAL to reach durable storage during527 bootstrapping.</td></tr><tr><td><code class="literal">WALBootstrapWrite</code></td><td>Waiting for a write of a WAL page during bootstrapping.</td></tr><tr><td><code class="literal">WALCopyRead</code></td><td>Waiting for a read when creating a new WAL segment by copying an528 existing one.</td></tr><tr><td><code class="literal">WALCopySync</code></td><td>Waiting for a new WAL segment created by copying an existing one to529 reach durable storage.</td></tr><tr><td><code class="literal">WALCopyWrite</code></td><td>Waiting for a write when creating a new WAL segment by copying an530 existing one.</td></tr><tr><td><code class="literal">WALInitSync</code></td><td>Waiting for a newly initialized WAL file to reach durable531 storage.</td></tr><tr><td><code class="literal">WALInitWrite</code></td><td>Waiting for a write while initializing a new WAL file.</td></tr><tr><td><code class="literal">WALRead</code></td><td>Waiting for a read from a WAL file.</td></tr><tr><td><code class="literal">WALSenderTimelineHistoryRead</code></td><td>Waiting for a read from a timeline history file during a walsender532 timeline command.</td></tr><tr><td><code class="literal">WALSync</code></td><td>Waiting for a WAL file to reach durable storage.</td></tr><tr><td><code class="literal">WALSyncMethodAssign</code></td><td>Waiting for data to reach durable storage while assigning a new533 WAL sync method.</td></tr><tr><td><code class="literal">WALWrite</code></td><td>Waiting for a write to a WAL file.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="WAIT-EVENT-IPC-TABLE"><p class="title"><strong>Table 28.10. Wait Events of Type <code class="literal">IPC</code></strong></p><div class="table-contents"><table class="table" summary="Wait Events of Type IPC" border="1"><colgroup><col /><col /></colgroup><thead><tr><th><code class="literal">IPC</code> Wait Event</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">AppendReady</code></td><td>Waiting for subplan nodes of an <code class="literal">Append</code> plan534 node to be ready.</td></tr><tr><td><code class="literal">ArchiveCleanupCommand</code></td><td>Waiting for <a class="xref" href="runtime-config-wal.html#GUC-ARCHIVE-CLEANUP-COMMAND">archive_cleanup_command</a> to535 complete.</td></tr><tr><td><code class="literal">ArchiveCommand</code></td><td>Waiting for <a class="xref" href="runtime-config-wal.html#GUC-ARCHIVE-COMMAND">archive_command</a> to536 complete.</td></tr><tr><td><code class="literal">BackendTermination</code></td><td>Waiting for the termination of another backend.</td></tr><tr><td><code class="literal">BackupWaitWalArchive</code></td><td>Waiting for WAL files required for a backup to be successfully537 archived.</td></tr><tr><td><code class="literal">BgWorkerShutdown</code></td><td>Waiting for background worker to shut down.</td></tr><tr><td><code class="literal">BgWorkerStartup</code></td><td>Waiting for background worker to start up.</td></tr><tr><td><code class="literal">BtreePage</code></td><td>Waiting for the page number needed to continue a parallel B-tree538 scan to become available.</td></tr><tr><td><code class="literal">BufferIO</code></td><td>Waiting for buffer I/O to complete.</td></tr><tr><td><code class="literal">CheckpointDone</code></td><td>Waiting for a checkpoint to complete.</td></tr><tr><td><code class="literal">CheckpointStart</code></td><td>Waiting for a checkpoint to start.</td></tr><tr><td><code class="literal">ExecuteGather</code></td><td>Waiting for activity from a child process while539 executing a <code class="literal">Gather</code> plan node.</td></tr><tr><td><code class="literal">HashBatchAllocate</code></td><td>Waiting for an elected Parallel Hash participant to allocate a hash540 table.</td></tr><tr><td><code class="literal">HashBatchElect</code></td><td>Waiting to elect a Parallel Hash participant to allocate a hash541 table.</td></tr><tr><td><code class="literal">HashBatchLoad</code></td><td>Waiting for other Parallel Hash participants to finish loading a542 hash table.</td></tr><tr><td><code class="literal">HashBuildAllocate</code></td><td>Waiting for an elected Parallel Hash participant to allocate the543 initial hash table.</td></tr><tr><td><code class="literal">HashBuildElect</code></td><td>Waiting to elect a Parallel Hash participant to allocate the544 initial hash table.</td></tr><tr><td><code class="literal">HashBuildHashInner</code></td><td>Waiting for other Parallel Hash participants to finish hashing the545 inner relation.</td></tr><tr><td><code class="literal">HashBuildHashOuter</code></td><td>Waiting for other Parallel Hash participants to finish partitioning546 the outer relation.</td></tr><tr><td><code class="literal">HashGrowBatchesDecide</code></td><td>Waiting to elect a Parallel Hash participant to decide on future547 batch growth.</td></tr><tr><td><code class="literal">HashGrowBatchesElect</code></td><td>Waiting to elect a Parallel Hash participant to allocate more548 batches.</td></tr><tr><td><code class="literal">HashGrowBatchesFinish</code></td><td>Waiting for an elected Parallel Hash participant to decide on549 future batch growth.</td></tr><tr><td><code class="literal">HashGrowBatchesReallocate</code></td><td>Waiting for an elected Parallel Hash participant to allocate more550 batches.</td></tr><tr><td><code class="literal">HashGrowBatchesRepartition</code></td><td>Waiting for other Parallel Hash participants to finish551 repartitioning.</td></tr><tr><td><code class="literal">HashGrowBucketsElect</code></td><td>Waiting to elect a Parallel Hash participant to allocate more552 buckets.</td></tr><tr><td><code class="literal">HashGrowBucketsReallocate</code></td><td>Waiting for an elected Parallel Hash participant to finish553 allocating more buckets.</td></tr><tr><td><code class="literal">HashGrowBucketsReinsert</code></td><td>Waiting for other Parallel Hash participants to finish inserting554 tuples into new buckets.</td></tr><tr><td><code class="literal">LogicalApplySendData</code></td><td>Waiting for a logical replication leader apply process to send555 data to a parallel apply process.</td></tr><tr><td><code class="literal">LogicalParallelApplyStateChange</code></td><td>Waiting for a logical replication parallel apply process to change556 state.</td></tr><tr><td><code class="literal">LogicalSyncData</code></td><td>Waiting for a logical replication remote server to send data for557 initial table synchronization.</td></tr><tr><td><code class="literal">LogicalSyncStateChange</code></td><td>Waiting for a logical replication remote server to change558 state.</td></tr><tr><td><code class="literal">MessageQueueInternal</code></td><td>Waiting for another process to be attached to a shared message559 queue.</td></tr><tr><td><code class="literal">MessageQueuePutMessage</code></td><td>Waiting to write a protocol message to a shared message queue.</td></tr><tr><td><code class="literal">MessageQueueReceive</code></td><td>Waiting to receive bytes from a shared message queue.</td></tr><tr><td><code class="literal">MessageQueueSend</code></td><td>Waiting to send bytes to a shared message queue.</td></tr><tr><td><code class="literal">ParallelBitmapScan</code></td><td>Waiting for parallel bitmap scan to become initialized.</td></tr><tr><td><code class="literal">ParallelCreateIndexScan</code></td><td>Waiting for parallel <code class="command">CREATE INDEX</code> workers to560 finish heap scan.</td></tr><tr><td><code class="literal">ParallelFinish</code></td><td>Waiting for parallel workers to finish computing.</td></tr><tr><td><code class="literal">ProcArrayGroupUpdate</code></td><td>Waiting for the group leader to clear the transaction ID at561 end of a parallel operation.</td></tr><tr><td><code class="literal">ProcSignalBarrier</code></td><td>Waiting for a barrier event to be processed by all562 backends.</td></tr><tr><td><code class="literal">Promote</code></td><td>Waiting for standby promotion.</td></tr><tr><td><code class="literal">RecoveryConflictSnapshot</code></td><td>Waiting for recovery conflict resolution for a vacuum563 cleanup.</td></tr><tr><td><code class="literal">RecoveryConflictTablespace</code></td><td>Waiting for recovery conflict resolution for dropping a564 tablespace.</td></tr><tr><td><code class="literal">RecoveryEndCommand</code></td><td>Waiting for <a class="xref" href="runtime-config-wal.html#GUC-RECOVERY-END-COMMAND">recovery_end_command</a> to565 complete.</td></tr><tr><td><code class="literal">RecoveryPause</code></td><td>Waiting for recovery to be resumed.</td></tr><tr><td><code class="literal">ReplicationOriginDrop</code></td><td>Waiting for a replication origin to become inactive so it can be566 dropped.</td></tr><tr><td><code class="literal">ReplicationSlotDrop</code></td><td>Waiting for a replication slot to become inactive so it can be567 dropped.</td></tr><tr><td><code class="literal">RestoreCommand</code></td><td>Waiting for <a class="xref" href="runtime-config-wal.html#GUC-RESTORE-COMMAND">restore_command</a> to568 complete.</td></tr><tr><td><code class="literal">SafeSnapshot</code></td><td>Waiting to obtain a valid snapshot for a <code class="literal">READ ONLY569 DEFERRABLE</code> transaction.</td></tr><tr><td><code class="literal">SyncRep</code></td><td>Waiting for confirmation from a remote server during synchronous570 replication.</td></tr><tr><td><code class="literal">WalReceiverExit</code></td><td>Waiting for the WAL receiver to exit.</td></tr><tr><td><code class="literal">WalReceiverWaitStart</code></td><td>Waiting for startup process to send initial data for streaming571 replication.</td></tr><tr><td><code class="literal">XactGroupUpdate</code></td><td>Waiting for the group leader to update transaction status at572 end of a parallel operation.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="WAIT-EVENT-LOCK-TABLE"><p class="title"><strong>Table 28.11. Wait Events of Type <code class="literal">Lock</code></strong></p><div class="table-contents"><table class="table" summary="Wait Events of Type Lock" border="1"><colgroup><col /><col /></colgroup><thead><tr><th><code class="literal">Lock</code> Wait Event</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">advisory</code></td><td>Waiting to acquire an advisory user lock.</td></tr><tr><td><code class="literal">applytransaction</code></td><td>Waiting to acquire a lock on a remote transaction being applied573 by a logical replication subscriber.</td></tr><tr><td><code class="literal">extend</code></td><td>Waiting to extend a relation.</td></tr><tr><td><code class="literal">frozenid</code></td><td>Waiting to574 update <code class="structname">pg_database</code>.<code class="structfield">datfrozenxid</code>575 and <code class="structname">pg_database</code>.<code class="structfield">datminmxid</code>.</td></tr><tr><td><code class="literal">object</code></td><td>Waiting to acquire a lock on a non-relation database object.</td></tr><tr><td><code class="literal">page</code></td><td>Waiting to acquire a lock on a page of a relation.</td></tr><tr><td><code class="literal">relation</code></td><td>Waiting to acquire a lock on a relation.</td></tr><tr><td><code class="literal">spectoken</code></td><td>Waiting to acquire a speculative insertion lock.</td></tr><tr><td><code class="literal">transactionid</code></td><td>Waiting for a transaction to finish.</td></tr><tr><td><code class="literal">tuple</code></td><td>Waiting to acquire a lock on a tuple.</td></tr><tr><td><code class="literal">userlock</code></td><td>Waiting to acquire a user lock.</td></tr><tr><td><code class="literal">virtualxid</code></td><td>Waiting to acquire a virtual transaction ID lock; see576 <a class="xref" href="transaction-id.html" title="74.1. Transactions and Identifiers">Section 74.1</a>.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="WAIT-EVENT-LWLOCK-TABLE"><p class="title"><strong>Table 28.12. Wait Events of Type <code class="literal">LWLock</code></strong></p><div class="table-contents"><table class="table" summary="Wait Events of Type LWLock" border="1"><colgroup><col /><col /></colgroup><thead><tr><th><code class="literal">LWLock</code> Wait Event</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">AddinShmemInit</code></td><td>Waiting to manage an extension's space allocation in shared577 memory.</td></tr><tr><td><code class="literal">AutoFile</code></td><td>Waiting to update the <code class="filename">postgresql.auto.conf</code>578 file.</td></tr><tr><td><code class="literal">Autovacuum</code></td><td>Waiting to read or update the current state of autovacuum579 workers.</td></tr><tr><td><code class="literal">AutovacuumSchedule</code></td><td>Waiting to ensure that a table selected for autovacuum580 still needs vacuuming.</td></tr><tr><td><code class="literal">BackgroundWorker</code></td><td>Waiting to read or update background worker state.</td></tr><tr><td><code class="literal">BtreeVacuum</code></td><td>Waiting to read or update vacuum-related information for a581 B-tree index.</td></tr><tr><td><code class="literal">BufferContent</code></td><td>Waiting to access a data page in memory.</td></tr><tr><td><code class="literal">BufferMapping</code></td><td>Waiting to associate a data block with a buffer in the buffer582 pool.</td></tr><tr><td><code class="literal">CheckpointerComm</code></td><td>Waiting to manage fsync requests.</td></tr><tr><td><code class="literal">CommitTs</code></td><td>Waiting to read or update the last value set for a583 transaction commit timestamp.</td></tr><tr><td><code class="literal">CommitTsBuffer</code></td><td>Waiting for I/O on a commit timestamp SLRU buffer.</td></tr><tr><td><code class="literal">CommitTsSLRU</code></td><td>Waiting to access the commit timestamp SLRU cache.</td></tr><tr><td><code class="literal">ControlFile</code></td><td>Waiting to read or update the <code class="filename">pg_control</code>584 file or create a new WAL file.</td></tr><tr><td><code class="literal">DynamicSharedMemoryControl</code></td><td>Waiting to read or update dynamic shared memory allocation585 information.</td></tr><tr><td><code class="literal">LockFastPath</code></td><td>Waiting to read or update a process' fast-path lock586 information.</td></tr><tr><td><code class="literal">LockManager</code></td><td>Waiting to read or update information587 about <span class="quote">“<span class="quote">heavyweight</span>”</span> locks.</td></tr><tr><td><code class="literal">LogicalRepLauncherDSA</code></td><td>Waiting to access logical replication launcher's dynamic shared588 memory allocator.</td></tr><tr><td><code class="literal">LogicalRepLauncherHash</code></td><td>Waiting to access logical replication launcher's shared589 hash table.</td></tr><tr><td><code class="literal">LogicalRepWorker</code></td><td>Waiting to read or update the state of logical replication590 workers.</td></tr><tr><td><code class="literal">MultiXactGen</code></td><td>Waiting to read or update shared multixact state.</td></tr><tr><td><code class="literal">MultiXactMemberBuffer</code></td><td>Waiting for I/O on a multixact member SLRU buffer.</td></tr><tr><td><code class="literal">MultiXactMemberSLRU</code></td><td>Waiting to access the multixact member SLRU cache.</td></tr><tr><td><code class="literal">MultiXactOffsetBuffer</code></td><td>Waiting for I/O on a multixact offset SLRU buffer.</td></tr><tr><td><code class="literal">MultiXactOffsetSLRU</code></td><td>Waiting to access the multixact offset SLRU cache.</td></tr><tr><td><code class="literal">MultiXactTruncation</code></td><td>Waiting to read or truncate multixact information.</td></tr><tr><td><code class="literal">NotifyBuffer</code></td><td>Waiting for I/O on a <code class="command">NOTIFY</code> message SLRU591 buffer.</td></tr><tr><td><code class="literal">NotifyQueue</code></td><td>Waiting to read or update <code class="command">NOTIFY</code> messages.</td></tr><tr><td><code class="literal">NotifyQueueTail</code></td><td>Waiting to update limit on <code class="command">NOTIFY</code> message592 storage.</td></tr><tr><td><code class="literal">NotifySLRU</code></td><td>Waiting to access the <code class="command">NOTIFY</code> message SLRU593 cache.</td></tr><tr><td><code class="literal">OidGen</code></td><td>Waiting to allocate a new OID.</td></tr><tr><td><code class="literal">OldSnapshotTimeMap</code></td><td>Waiting to read or update old snapshot control information.</td></tr><tr><td><code class="literal">ParallelAppend</code></td><td>Waiting to choose the next subplan during Parallel Append plan594 execution.</td></tr><tr><td><code class="literal">ParallelHashJoin</code></td><td>Waiting to synchronize workers during Parallel Hash Join plan595 execution.</td></tr><tr><td><code class="literal">ParallelQueryDSA</code></td><td>Waiting for parallel query dynamic shared memory allocation.</td></tr><tr><td><code class="literal">PerSessionDSA</code></td><td>Waiting for parallel query dynamic shared memory allocation.</td></tr><tr><td><code class="literal">PerSessionRecordType</code></td><td>Waiting to access a parallel query's information about composite596 types.</td></tr><tr><td><code class="literal">PerSessionRecordTypmod</code></td><td>Waiting to access a parallel query's information about type597 modifiers that identify anonymous record types.</td></tr><tr><td><code class="literal">PerXactPredicateList</code></td><td>Waiting to access the list of predicate locks held by the current598 serializable transaction during a parallel query.</td></tr><tr><td><code class="literal">PgStatsData</code></td><td>Waiting for shared memory stats data access</td></tr><tr><td><code class="literal">PgStatsDSA</code></td><td>Waiting for stats dynamic shared memory allocator access</td></tr><tr><td><code class="literal">PgStatsHash</code></td><td>Waiting for stats shared memory hash table access</td></tr><tr><td><code class="literal">PredicateLockManager</code></td><td>Waiting to access predicate lock information used by599 serializable transactions.</td></tr><tr><td><code class="literal">ProcArray</code></td><td>Waiting to access the shared per-process data structures600 (typically, to get a snapshot or report a session's transaction601 ID).</td></tr><tr><td><code class="literal">RelationMapping</code></td><td>Waiting to read or update602 a <code class="filename">pg_filenode.map</code> file (used to track the603 filenode assignments of certain system catalogs).</td></tr><tr><td><code class="literal">RelCacheInit</code></td><td>Waiting to read or update a <code class="filename">pg_internal.init</code>604 relation cache initialization file.</td></tr><tr><td><code class="literal">ReplicationOrigin</code></td><td>Waiting to create, drop or use a replication origin.</td></tr><tr><td><code class="literal">ReplicationOriginState</code></td><td>Waiting to read or update the progress of one replication605 origin.</td></tr><tr><td><code class="literal">ReplicationSlotAllocation</code></td><td>Waiting to allocate or free a replication slot.</td></tr><tr><td><code class="literal">ReplicationSlotControl</code></td><td>Waiting to read or update replication slot state.</td></tr><tr><td><code class="literal">ReplicationSlotIO</code></td><td>Waiting for I/O on a replication slot.</td></tr><tr><td><code class="literal">SerialBuffer</code></td><td>Waiting for I/O on a serializable transaction conflict SLRU606 buffer.</td></tr><tr><td><code class="literal">SerializableFinishedList</code></td><td>Waiting to access the list of finished serializable607 transactions.</td></tr><tr><td><code class="literal">SerializablePredicateList</code></td><td>Waiting to access the list of predicate locks held by608 serializable transactions.</td></tr><tr><td><code class="literal">SerializableXactHash</code></td><td>Waiting to read or update information about serializable609 transactions.</td></tr><tr><td><code class="literal">SerialSLRU</code></td><td>Waiting to access the serializable transaction conflict SLRU610 cache.</td></tr><tr><td><code class="literal">SharedTidBitmap</code></td><td>Waiting to access a shared TID bitmap during a parallel bitmap611 index scan.</td></tr><tr><td><code class="literal">SharedTupleStore</code></td><td>Waiting to access a shared tuple store during parallel612 query.</td></tr><tr><td><code class="literal">ShmemIndex</code></td><td>Waiting to find or allocate space in shared memory.</td></tr><tr><td><code class="literal">SInvalRead</code></td><td>Waiting to retrieve messages from the shared catalog invalidation613 queue.</td></tr><tr><td><code class="literal">SInvalWrite</code></td><td>Waiting to add a message to the shared catalog invalidation614 queue.</td></tr><tr><td><code class="literal">SubtransBuffer</code></td><td>Waiting for I/O on a sub-transaction SLRU buffer.</td></tr><tr><td><code class="literal">SubtransSLRU</code></td><td>Waiting to access the sub-transaction SLRU cache.</td></tr><tr><td><code class="literal">SyncRep</code></td><td>Waiting to read or update information about the state of615 synchronous replication.</td></tr><tr><td><code class="literal">SyncScan</code></td><td>Waiting to select the starting location of a synchronized table616 scan.</td></tr><tr><td><code class="literal">TablespaceCreate</code></td><td>Waiting to create or drop a tablespace.</td></tr><tr><td><code class="literal">TwoPhaseState</code></td><td>Waiting to read or update the state of prepared transactions.</td></tr><tr><td><code class="literal">WALBufMapping</code></td><td>Waiting to replace a page in WAL buffers.</td></tr><tr><td><code class="literal">WALInsert</code></td><td>Waiting to insert WAL data into a memory buffer.</td></tr><tr><td><code class="literal">WALWrite</code></td><td>Waiting for WAL buffers to be written to disk.</td></tr><tr><td><code class="literal">WrapLimitsVacuum</code></td><td>Waiting to update limits on transaction id and multixact617 consumption.</td></tr><tr><td><code class="literal">XactBuffer</code></td><td>Waiting for I/O on a transaction status SLRU buffer.</td></tr><tr><td><code class="literal">XactSLRU</code></td><td>Waiting to access the transaction status SLRU cache.</td></tr><tr><td><code class="literal">XactTruncation</code></td><td>Waiting to execute <code class="function">pg_xact_status</code> or update618 the oldest transaction ID available to it.</td></tr><tr><td><code class="literal">XidGen</code></td><td>Waiting to allocate a new transaction ID.</td></tr></tbody></table></div></div><br class="table-break" /><div class="note"><h3 class="title">Note</h3><p>619 Extensions can add <code class="literal">LWLock</code> types to the list shown in620 <a class="xref" href="monitoring-stats.html#WAIT-EVENT-LWLOCK-TABLE" title="Table 28.12. Wait Events of Type LWLock">Table 28.12</a>. In some cases, the name621 assigned by an extension will not be available in all server processes;622 so an <code class="literal">LWLock</code> wait event might be reported as623 just <span class="quote">“<span class="quote"><code class="literal">extension</code></span>”</span> rather than the624 extension-assigned name.625 </p></div><div class="table" id="WAIT-EVENT-TIMEOUT-TABLE"><p class="title"><strong>Table 28.13. Wait Events of Type <code class="literal">Timeout</code></strong></p><div class="table-contents"><table class="table" summary="Wait Events of Type Timeout" border="1"><colgroup><col /><col /></colgroup><thead><tr><th><code class="literal">Timeout</code> Wait Event</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">BaseBackupThrottle</code></td><td>Waiting during base backup when throttling activity.</td></tr><tr><td><code class="literal">CheckpointWriteDelay</code></td><td>Waiting between writes while performing a checkpoint.</td></tr><tr><td><code class="literal">PgSleep</code></td><td>Waiting due to a call to <code class="function">pg_sleep</code> or626 a sibling function.</td></tr><tr><td><code class="literal">RecoveryApplyDelay</code></td><td>Waiting to apply WAL during recovery because of a delay627 setting.</td></tr><tr><td><code class="literal">RecoveryRetrieveRetryInterval</code></td><td>Waiting during recovery when WAL data is not available from any628 source (<code class="filename">pg_wal</code>, archive or stream).</td></tr><tr><td><code class="literal">RegisterSyncRequest</code></td><td>Waiting while sending synchronization requests to the629 checkpointer, because the request queue is full.</td></tr><tr><td><code class="literal">SpinDelay</code></td><td>Waiting while acquiring a contended spinlock.</td></tr><tr><td><code class="literal">VacuumDelay</code></td><td>Waiting in a cost-based vacuum delay point.</td></tr><tr><td><code class="literal">VacuumTruncate</code></td><td>Waiting to acquire an exclusive lock to truncate off any630 empty pages at the end of a table vacuumed.</td></tr></tbody></table></div></div><br class="table-break" /><p>631 Here is an example of how wait events can be viewed:632 633</p><pre class="programlisting">634SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event is NOT NULL;635 pid | wait_event_type | wait_event636------+-----------------+------------637 2540 | Lock | relation638 6644 | LWLock | ProcArray639(2 rows)640</pre><p>641 </p></div><div class="sect2" id="MONITORING-PG-STAT-REPLICATION-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.4. <code class="structname">pg_stat_replication</code> <a href="#MONITORING-PG-STAT-REPLICATION-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.15.7.8.2" class="indexterm"></a><p>642 The <code class="structname">pg_stat_replication</code> view will contain one row643 per WAL sender process, showing statistics about replication to that644 sender's connected standby server. Only directly connected standbys are645 listed; no information is available about downstream standby servers.646 </p><div class="table" id="PG-STAT-REPLICATION-VIEW"><p class="title"><strong>Table 28.14. <code class="structname">pg_stat_replication</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_replication View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">647 Column Type648 </p>649 <p>650 Description651 </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">652 <code class="structfield">pid</code> <code class="type">integer</code>653 </p>654 <p>655 Process ID of a WAL sender process656 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">657 <code class="structfield">usesysid</code> <code class="type">oid</code>658 </p>659 <p>660 OID of the user logged into this WAL sender process661 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">662 <code class="structfield">usename</code> <code class="type">name</code>663 </p>664 <p>665 Name of the user logged into this WAL sender process666 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">667 <code class="structfield">application_name</code> <code class="type">text</code>668 </p>669 <p>670 Name of the application that is connected671 to this WAL sender672 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">673 <code class="structfield">client_addr</code> <code class="type">inet</code>674 </p>675 <p>676 IP address of the client connected to this WAL sender.677 If this field is null, it indicates that the client is678 connected via a Unix socket on the server machine.679 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">680 <code class="structfield">client_hostname</code> <code class="type">text</code>681 </p>682 <p>683 Host name of the connected client, as reported by a684 reverse DNS lookup of <code class="structfield">client_addr</code>. This field will685 only be non-null for IP connections, and only when <a class="xref" href="runtime-config-logging.html#GUC-LOG-HOSTNAME">log_hostname</a> is enabled.686 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">687 <code class="structfield">client_port</code> <code class="type">integer</code>688 </p>689 <p>690 TCP port number that the client is using for communication691 with this WAL sender, or <code class="literal">-1</code> if a Unix socket is used692 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">693 <code class="structfield">backend_start</code> <code class="type">timestamp with time zone</code>694 </p>695 <p>696 Time when this process was started, i.e., when the697 client connected to this WAL sender698 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">699 <code class="structfield">backend_xmin</code> <code class="type">xid</code>700 </p>701 <p>702 This standby's <code class="literal">xmin</code> horizon reported703 by <a class="xref" href="runtime-config-replication.html#GUC-HOT-STANDBY-FEEDBACK">hot_standby_feedback</a>.704 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">705 <code class="structfield">state</code> <code class="type">text</code>706 </p>707 <p>708 Current WAL sender state.709 Possible values are:710 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>711 <code class="literal">startup</code>: This WAL sender is starting up.712 </p></li><li class="listitem"><p>713 <code class="literal">catchup</code>: This WAL sender's connected standby is714 catching up with the primary.715 </p></li><li class="listitem"><p>716 <code class="literal">streaming</code>: This WAL sender is streaming changes717 after its connected standby server has caught up with the primary.718 </p></li><li class="listitem"><p>719 <code class="literal">backup</code>: This WAL sender is sending a backup.720 </p></li><li class="listitem"><p>721 <code class="literal">stopping</code>: This WAL sender is stopping.722 </p></li></ul></div><p>723 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">724 <code class="structfield">sent_lsn</code> <code class="type">pg_lsn</code>725 </p>726 <p>727 Last write-ahead log location sent on this connection728 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">729 <code class="structfield">write_lsn</code> <code class="type">pg_lsn</code>730 </p>731 <p>732 Last write-ahead log location written to disk by this standby733 server734 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">735 <code class="structfield">flush_lsn</code> <code class="type">pg_lsn</code>736 </p>737 <p>738 Last write-ahead log location flushed to disk by this standby739 server740 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">741 <code class="structfield">replay_lsn</code> <code class="type">pg_lsn</code>742 </p>743 <p>744 Last write-ahead log location replayed into the database on this745 standby server746 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">747 <code class="structfield">write_lag</code> <code class="type">interval</code>748 </p>749 <p>750 Time elapsed between flushing recent WAL locally and receiving751 notification that this standby server has written it (but not yet752 flushed it or applied it). This can be used to gauge the delay that753 <code class="literal">synchronous_commit</code> level754 <code class="literal">remote_write</code> incurred while committing if this755 server was configured as a synchronous standby.756 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">757 <code class="structfield">flush_lag</code> <code class="type">interval</code>758 </p>759 <p>760 Time elapsed between flushing recent WAL locally and receiving761 notification that this standby server has written and flushed it762 (but not yet applied it). This can be used to gauge the delay that763 <code class="literal">synchronous_commit</code> level764 <code class="literal">on</code> incurred while committing if this765 server was configured as a synchronous standby.766 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">767 <code class="structfield">replay_lag</code> <code class="type">interval</code>768 </p>769 <p>770 Time elapsed between flushing recent WAL locally and receiving771 notification that this standby server has written, flushed and772 applied it. This can be used to gauge the delay that773 <code class="literal">synchronous_commit</code> level774 <code class="literal">remote_apply</code> incurred while committing if this775 server was configured as a synchronous standby.776 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">777 <code class="structfield">sync_priority</code> <code class="type">integer</code>778 </p>779 <p>780 Priority of this standby server for being chosen as the781 synchronous standby in a priority-based synchronous replication.782 This has no effect in a quorum-based synchronous replication.783 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">784 <code class="structfield">sync_state</code> <code class="type">text</code>785 </p>786 <p>787 Synchronous state of this standby server.788 Possible values are:789 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>790 <code class="literal">async</code>: This standby server is asynchronous.791 </p></li><li class="listitem"><p>792 <code class="literal">potential</code>: This standby server is now asynchronous,793 but can potentially become synchronous if one of current794 synchronous ones fails.795 </p></li><li class="listitem"><p>796 <code class="literal">sync</code>: This standby server is synchronous.797 </p></li><li class="listitem"><p>798 <code class="literal">quorum</code>: This standby server is considered as a candidate799 for quorum standbys.800 </p></li></ul></div><p>801 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">802 <code class="structfield">reply_time</code> <code class="type">timestamp with time zone</code>803 </p>804 <p>805 Send time of last reply message received from standby server806 </p></td></tr></tbody></table></div></div><br class="table-break" /><p>807 The lag times reported in the <code class="structname">pg_stat_replication</code>808 view are measurements of the time taken for recent WAL to be written,809 flushed and replayed and for the sender to know about it. These times810 represent the commit delay that was (or would have been) introduced by each811 synchronous commit level, if the remote server was configured as a812 synchronous standby. For an asynchronous standby, the813 <code class="structfield">replay_lag</code> column approximates the delay814 before recent transactions became visible to queries. If the standby815 server has entirely caught up with the sending server and there is no more816 WAL activity, the most recently measured lag times will continue to be817 displayed for a short time and then show NULL.818 </p><p>819 Lag times work automatically for physical replication. Logical decoding820 plugins may optionally emit tracking messages; if they do not, the tracking821 mechanism will simply display NULL lag.822 </p><div class="note"><h3 class="title">Note</h3><p>823 The reported lag times are not predictions of how long it will take for824 the standby to catch up with the sending server assuming the current825 rate of replay. Such a system would show similar times while new WAL is826 being generated, but would differ when the sender becomes idle. In827 particular, when the standby has caught up completely,828 <code class="structname">pg_stat_replication</code> shows the time taken to829 write, flush and replay the most recent reported WAL location rather than830 zero as some users might expect. This is consistent with the goal of831 measuring synchronous commit and transaction visibility delays for832 recent write transactions.833 To reduce confusion for users expecting a different model of lag, the834 lag columns revert to NULL after a short time on a fully replayed idle835 system. Monitoring systems should choose whether to represent this836 as missing data, zero or continue to display the last known value.837 </p></div></div><div class="sect2" id="MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.5. <code class="structname">pg_stat_replication_slots</code> <a href="#MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.15.7.9.2" class="indexterm"></a><p>838 The <code class="structname">pg_stat_replication_slots</code> view will contain839 one row per logical replication slot, showing statistics about its usage.840 </p><div class="table" id="PG-STAT-REPLICATION-SLOTS-VIEW"><p class="title"><strong>Table 28.15. <code class="structname">pg_stat_replication_slots</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_replication_slots View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">841 Column Type842 </p>843 <p>844 Description845 </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">846 <code class="structfield">slot_name</code> <code class="type">text</code>847 </p>848 <p>849 A unique, cluster-wide identifier for the replication slot850 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">851 <code class="structfield">spill_txns</code> <code class="type">bigint</code>852 </p>853 <p>854 Number of transactions spilled to disk once the memory used by855 logical decoding to decode changes from WAL has exceeded856 <code class="literal">logical_decoding_work_mem</code>. The counter gets857 incremented for both top-level transactions and subtransactions.858 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">859 <code class="structfield">spill_count</code> <code class="type">bigint</code>860 </p>861 <p>862 Number of times transactions were spilled to disk while decoding863 changes from WAL for this slot. This counter is incremented each time864 a transaction is spilled, and the same transaction may be spilled865 multiple times.866 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">867 <code class="structfield">spill_bytes</code> <code class="type">bigint</code>868 </p>869 <p>870 Amount of decoded transaction data spilled to disk while performing871 decoding of changes from WAL for this slot. This and other spill872 counters can be used to gauge the I/O which occurred during logical873 decoding and allow tuning <code class="literal">logical_decoding_work_mem</code>.874 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">875 <code class="structfield">stream_txns</code> <code class="type">bigint</code>876 </p>877 <p>878 Number of in-progress transactions streamed to the decoding output879 plugin after the memory used by logical decoding to decode changes880 from WAL for this slot has exceeded881 <code class="literal">logical_decoding_work_mem</code>. Streaming only882 works with top-level transactions (subtransactions can't be streamed883 independently), so the counter is not incremented for subtransactions.884 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">885 <code class="structfield">stream_count</code><code class="type">bigint</code>886 </p>887 <p>888 Number of times in-progress transactions were streamed to the decoding889 output plugin while decoding changes from WAL for this slot. This890 counter is incremented each time a transaction is streamed, and the891 same transaction may be streamed multiple times.892 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">893 <code class="structfield">stream_bytes</code><code class="type">bigint</code>894 </p>895 <p>896 Amount of transaction data decoded for streaming in-progress897 transactions to the decoding output plugin while decoding changes from898 WAL for this slot. This and other streaming counters for this slot can899 be used to tune <code class="literal">logical_decoding_work_mem</code>.900 </p>901 </td></tr><tr><td class="catalog_table_entry"><p class="column_definition">902 <code class="structfield">total_txns</code> <code class="type">bigint</code>903 </p>904 <p>905 Number of decoded transactions sent to the decoding output plugin for906 this slot. This counts top-level transactions only, and is not incremented907 for subtransactions. Note that this includes the transactions that are908 streamed and/or spilled.909 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">910 <code class="structfield">total_bytes</code><code class="type">bigint</code>911 </p>912 <p>913 Amount of transaction data decoded for sending transactions to the914 decoding output plugin while decoding changes from WAL for this slot.915 Note that this includes data that is streamed and/or spilled.916 </p>917 </td></tr><tr><td class="catalog_table_entry"><p class="column_definition">918 <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>919 </p>920 <p>921 Time at which these statistics were last reset922 </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-WAL-RECEIVER-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.6. <code class="structname">pg_stat_wal_receiver</code> <a href="#MONITORING-PG-STAT-WAL-RECEIVER-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.15.7.10.2" class="indexterm"></a><p>923 The <code class="structname">pg_stat_wal_receiver</code> view will contain only924 one row, showing statistics about the WAL receiver from that receiver's925 connected server.926 </p><div class="table" id="PG-STAT-WAL-RECEIVER-VIEW"><p class="title"><strong>Table 28.16. <code class="structname">pg_stat_wal_receiver</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_wal_receiver View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">927 Column Type928 </p>929 <p>930 Description931 </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">932 <code class="structfield">pid</code> <code class="type">integer</code>933 </p>934 <p>935 Process ID of the WAL receiver process936 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">937 <code class="structfield">status</code> <code class="type">text</code>938 </p>939 <p>940 Activity status of the WAL receiver process941 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">942 <code class="structfield">receive_start_lsn</code> <code class="type">pg_lsn</code>943 </p>944 <p>945 First write-ahead log location used when WAL receiver is946 started947 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">948 <code class="structfield">receive_start_tli</code> <code class="type">integer</code>949 </p>950 <p>951 First timeline number used when WAL receiver is started952 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">953 <code class="structfield">written_lsn</code> <code class="type">pg_lsn</code>954 </p>955 <p>956 Last write-ahead log location already received and written to disk,957 but not flushed. This should not be used for data integrity checks.958 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">959 <code class="structfield">flushed_lsn</code> <code class="type">pg_lsn</code>960 </p>961 <p>962 Last write-ahead log location already received and flushed to963 disk, the initial value of this field being the first log location used964 when WAL receiver is started965 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">966 <code class="structfield">received_tli</code> <code class="type">integer</code>967 </p>968 <p>969 Timeline number of last write-ahead log location received and970 flushed to disk, the initial value of this field being the timeline971 number of the first log location used when WAL receiver is started972 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">973 <code class="structfield">last_msg_send_time</code> <code class="type">timestamp with time zone</code>974 </p>975 <p>976 Send time of last message received from origin WAL sender977 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">978 <code class="structfield">last_msg_receipt_time</code> <code class="type">timestamp with time zone</code>979 </p>980 <p>981 Receipt time of last message received from origin WAL sender982 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">983 <code class="structfield">latest_end_lsn</code> <code class="type">pg_lsn</code>984 </p>985 <p>986 Last write-ahead log location reported to origin WAL sender987 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">988 <code class="structfield">latest_end_time</code> <code class="type">timestamp with time zone</code>989 </p>990 <p>991 Time of last write-ahead log location reported to origin WAL sender992 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">993 <code class="structfield">slot_name</code> <code class="type">text</code>994 </p>995 <p>996 Replication slot name used by this WAL receiver997 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">998 <code class="structfield">sender_host</code> <code class="type">text</code>999 </p>1000 <p>1001 Host of the <span class="productname">PostgreSQL</span> instance1002 this WAL receiver is connected to. This can be a host name,1003 an IP address, or a directory path if the connection is via1004 Unix socket. (The path case can be distinguished because it1005 will always be an absolute path, beginning with <code class="literal">/</code>.)1006 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1007 <code class="structfield">sender_port</code> <code class="type">integer</code>1008 </p>1009 <p>1010 Port number of the <span class="productname">PostgreSQL</span> instance1011 this WAL receiver is connected to.1012 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1013 <code class="structfield">conninfo</code> <code class="type">text</code>1014 </p>1015 <p>1016 Connection string used by this WAL receiver,1017 with security-sensitive fields obfuscated.1018 </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-RECOVERY-PREFETCH"><div class="titlepage"><div><div><h3 class="title">28.2.7. <code class="structname">pg_stat_recovery_prefetch</code> <a href="#MONITORING-PG-STAT-RECOVERY-PREFETCH" class="id_link">#</a></h3></div></div></div><a id="id-1.6.15.7.11.2" class="indexterm"></a><p>1019 The <code class="structname">pg_stat_recovery_prefetch</code> view will contain1020 only one row. The columns <code class="structfield">wal_distance</code>,1021 <code class="structfield">block_distance</code> and1022 <code class="structfield">io_depth</code> show current values, and the1023 other columns show cumulative counters that can be reset1024 with the <code class="function">pg_stat_reset_shared</code> function.1025 </p><div class="table" id="PG-STAT-RECOVERY-PREFETCH-VIEW"><p class="title"><strong>Table 28.17. <code class="structname">pg_stat_recovery_prefetch</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_recovery_prefetch View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">1026 Column Type1027 </p>1028 <p>1029 Description1030 </p></th></tr></thead><tbody><tr><td class="catalog_table_entry">1031 <p class="column_definition">1032 <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>1033 </p>1034 <p>1035 Time at which these statistics were last reset1036 </p>1037 </td></tr><tr><td class="catalog_table_entry">1038 <p class="column_definition">1039 <code class="structfield">prefetch</code> <code class="type">bigint</code>1040 </p>1041 <p>1042 Number of blocks prefetched because they were not in the buffer pool1043 </p>1044 </td></tr><tr><td class="catalog_table_entry">1045 <p class="column_definition">1046 <code class="structfield">hit</code> <code class="type">bigint</code>1047 </p>1048 <p>1049 Number of blocks not prefetched because they were already in the buffer pool1050 </p>1051 </td></tr><tr><td class="catalog_table_entry">1052 <p class="column_definition">1053 <code class="structfield">skip_init</code> <code class="type">bigint</code>1054 </p>1055 <p>1056 Number of blocks not prefetched because they would be zero-initialized1057 </p>1058 </td></tr><tr><td class="catalog_table_entry">1059 <p class="column_definition">1060 <code class="structfield">skip_new</code> <code class="type">bigint</code>1061 </p>1062 <p>1063 Number of blocks not prefetched because they didn't exist yet1064 </p>1065 </td></tr><tr><td class="catalog_table_entry">1066 <p class="column_definition">1067 <code class="structfield">skip_fpw</code> <code class="type">bigint</code>1068 </p>1069 <p>1070 Number of blocks not prefetched because a full page image was included in the WAL1071 </p>1072 </td></tr><tr><td class="catalog_table_entry">1073 <p class="column_definition">1074 <code class="structfield">skip_rep</code> <code class="type">bigint</code>1075 </p>1076 <p>1077 Number of blocks not prefetched because they were already recently prefetched1078 </p>1079 </td></tr><tr><td class="catalog_table_entry">1080 <p class="column_definition">1081 <code class="structfield">wal_distance</code> <code class="type">int</code>1082 </p>1083 <p>1084 How many bytes ahead the prefetcher is looking1085 </p>1086 </td></tr><tr><td class="catalog_table_entry">1087 <p class="column_definition">1088 <code class="structfield">block_distance</code> <code class="type">int</code>1089 </p>1090 <p>1091 How many blocks ahead the prefetcher is looking1092 </p>1093 </td></tr><tr><td class="catalog_table_entry">1094 <p class="column_definition">1095 <code class="structfield">io_depth</code> <code class="type">int</code>1096 </p>1097 <p>1098 How many prefetches have been initiated but are not yet known to have completed1099 </p>1100 </td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-SUBSCRIPTION"><div class="titlepage"><div><div><h3 class="title">28.2.8. <code class="structname">pg_stat_subscription</code> <a href="#MONITORING-PG-STAT-SUBSCRIPTION" class="id_link">#</a></h3></div></div></div><a id="id-1.6.15.7.12.2" class="indexterm"></a><div class="table" id="PG-STAT-SUBSCRIPTION"><p class="title"><strong>Table 28.18. <code class="structname">pg_stat_subscription</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_subscription View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">1101 Column Type1102 </p>1103 <p>1104 Description1105 </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">1106 <code class="structfield">subid</code> <code class="type">oid</code>1107 </p>1108 <p>1109 OID of the subscription1110 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1111 <code class="structfield">subname</code> <code class="type">name</code>1112 </p>1113 <p>1114 Name of the subscription1115 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1116 <code class="structfield">pid</code> <code class="type">integer</code>1117 </p>1118 <p>1119 Process ID of the subscription worker process1120 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1121 <code class="structfield">leader_pid</code> <code class="type">integer</code>1122 </p>1123 <p>1124 Process ID of the leader apply worker if this process is a parallel1125 apply worker; NULL if this process is a leader apply worker or a1126 synchronization worker1127 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1128 <code class="structfield">relid</code> <code class="type">oid</code>1129 </p>1130 <p>1131 OID of the relation that the worker is synchronizing; NULL for the1132 leader apply worker and parallel apply workers1133 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1134 <code class="structfield">received_lsn</code> <code class="type">pg_lsn</code>1135 </p>1136 <p>1137 Last write-ahead log location received, the initial value of1138 this field being 0; NULL for parallel apply workers1139 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1140 <code class="structfield">last_msg_send_time</code> <code class="type">timestamp with time zone</code>1141 </p>1142 <p>1143 Send time of last message received from origin WAL sender; NULL for1144 parallel apply workers1145 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1146 <code class="structfield">last_msg_receipt_time</code> <code class="type">timestamp with time zone</code>1147 </p>1148 <p>1149 Receipt time of last message received from origin WAL sender; NULL for1150 parallel apply workers1151 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1152 <code class="structfield">latest_end_lsn</code> <code class="type">pg_lsn</code>1153 </p>1154 <p>1155 Last write-ahead log location reported to origin WAL sender; NULL for1156 parallel apply workers1157 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1158 <code class="structfield">latest_end_time</code> <code class="type">timestamp with time zone</code>1159 </p>1160 <p>1161 Time of last write-ahead log location reported to origin WAL1162 sender; NULL for parallel apply workers1163 </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-SUBSCRIPTION-STATS"><div class="titlepage"><div><div><h3 class="title">28.2.9. <code class="structname">pg_stat_subscription_stats</code> <a href="#MONITORING-PG-STAT-SUBSCRIPTION-STATS" class="id_link">#</a></h3></div></div></div><a id="id-1.6.15.7.13.2" class="indexterm"></a><p>1164 The <code class="structname">pg_stat_subscription_stats</code> view will contain1165 one row per subscription.1166 </p><div class="table" id="PG-STAT-SUBSCRIPTION-STATS"><p class="title"><strong>Table 28.19. <code class="structname">pg_stat_subscription_stats</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_subscription_stats View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">1167 Column Type1168 </p>1169 <p>1170 Description1171 </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">1172 <code class="structfield">subid</code> <code class="type">oid</code>1173 </p>1174 <p>1175 OID of the subscription1176 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1177 <code class="structfield">subname</code> <code class="type">name</code>1178 </p>1179 <p>1180 Name of the subscription1181 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1182 <code class="structfield">apply_error_count</code> <code class="type">bigint</code>1183 </p>1184 <p>1185 Number of times an error occurred while applying changes1186 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1187 <code class="structfield">sync_error_count</code> <code class="type">bigint</code>1188 </p>1189 <p>1190 Number of times an error occurred during the initial table1191 synchronization1192 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">1193 <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>1194 </p>1195 <p>1196 Time at which these statistics were last reset1197 </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-SSL-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.10. <code class="structname">pg_stat_ssl</code> <a href="#MONITORING-PG-STAT-SSL-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.15.7.14.2" class="indexterm"></a><p>1198 The <code class="structname">pg_stat_ssl</code> view will contain one row per1199 backend or WAL sender process, showing statistics about SSL usage on1200 this connection. It can be joined to <code class="structname">pg_stat_activity</code>