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diff --git a/doc/src/sgml/html/monitoring-stats.html b/doc/src/sgml/html/monitoring-stats.html new file mode 100644 index 0000000..23cde4b --- /dev/null +++ b/doc/src/sgml/html/monitoring-stats.html @@ -0,0 +1,2470 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>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 15.4 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</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-BGWRITER-VIEW">28.2.13. <code class="structname">pg_stat_bgwriter</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW">28.2.14. <code class="structname">pg_stat_wal</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-VIEW">28.2.15. <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">28.2.16. <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">28.2.17. <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">28.2.18. <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">28.2.19. <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">28.2.20. <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">28.2.21. <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">28.2.22. <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">28.2.23. <code class="structname">pg_stat_slru</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-STATS-FUNCTIONS">28.2.24. Statistics Functions</a></span></dt></dl></div><a id="id-1.6.15.7.2" class="indexterm"></a><p> + <span class="productname">PostgreSQL</span>'s <em class="firstterm">cumulative statistics + system</em> supports collection and reporting of information about + server activity. Presently, accesses to tables and indexes in both + disk-block and individual-row terms are counted. The total number of rows + in each table, and information about vacuum and analyze actions for each + table are also counted. If enabled, calls to user-defined functions and + the total time spent in each one are counted as well. + </p><p> + <span class="productname">PostgreSQL</span> also supports reporting dynamic + information about exactly what is going on in the system right now, such as + the exact command currently being executed by other server processes, and + which other connections exist in the system. This facility is independent + of the cumulative statistics system. + </p><div class="sect2" id="MONITORING-STATS-SETUP"><div class="titlepage"><div><div><h3 class="title">28.2.1. Statistics Collection Configuration</h3></div></div></div><p> + Since collection of statistics adds some overhead to query execution, + the system can be configured to collect or not collect information. + This is controlled by configuration parameters that are normally set in + <code class="filename">postgresql.conf</code>. (See <a class="xref" href="runtime-config.html" title="Chapter 20. Server Configuration">Chapter 20</a> for + details about setting configuration parameters.) + </p><p> + The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-ACTIVITIES">track_activities</a> enables monitoring + of the current command being executed by any server process. + </p><p> + The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-COUNTS">track_counts</a> controls whether + cumulative statistics are collected about table and index accesses. + </p><p> + The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-FUNCTIONS">track_functions</a> enables tracking of + usage of user-defined functions. + </p><p> + The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> enables monitoring + of block read and write times. + </p><p> + The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-WAL-IO-TIMING">track_wal_io_timing</a> enables monitoring + of WAL write times. + </p><p> + Normally these parameters are set in <code class="filename">postgresql.conf</code> so + that they apply to all server processes, but it is possible to turn + 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 prevent + ordinary users from hiding their activity from the administrator, + only superusers are allowed to change these parameters with + <code class="command">SET</code>.) + </p><p> + Cumulative statistics are collected in shared memory. Every + <span class="productname">PostgreSQL</span> process collects statistics locally, + then updates the shared data at appropriate intervals. When a server, + including a physical replica, shuts down cleanly, a permanent copy of the + statistics data is stored in the <code class="filename">pg_stat</code> subdirectory, + so that statistics can be retained across server restarts. In contrast, + when starting from an unclean shutdown (e.g., after an immediate shutdown, + a server crash, starting from a base backup, and point-in-time recovery), + all statistics counters are reset. + </p></div><div class="sect2" id="MONITORING-STATS-VIEWS"><div class="titlepage"><div><div><h3 class="title">28.2.2. Viewing Statistics</h3></div></div></div><p> + 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 show + the current state of the system. There are also several other + 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 accumulated + statistics. Alternatively, one can + build custom views using the underlying cumulative statistics functions, as + discussed in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-FUNCTIONS" title="28.2.24. Statistics Functions">Section 28.2.24</a>. + </p><p> + When using the cumulative statistics views and functions to monitor + collected data, it is important to realize that the information does not + update instantaneously. Each individual server process flushes out + accumulated statistics to shared memory just before going idle, but not + more frequently than once per <code class="varname">PGSTAT_MIN_INTERVAL</code> + milliseconds (1 second unless altered while building the server); so a + query or transaction still in progress does not affect the displayed totals + and the displayed information lags behind actual activity. However, + current-query information collected by <code class="varname">track_activities</code> + is always up-to-date. + </p><p> + Another important point is that when a server process is asked to display + any of the accumulated statistics, accessed values are cached until the end + of its current transaction in the default configuration. So the statistics + will show static information as long as you continue the current + transaction. Similarly, information about the current queries of all + sessions is collected when any such information is first requested within a + transaction, and the same information will be displayed throughout the + transaction. This is a feature, not a bug, because it allows you to perform + several queries on the statistics and correlate the results without + worrying that the numbers are changing underneath you. + + When analyzing statistics interactively, or with expensive queries, the + time delta between accesses to individual statistics can lead to + significant skew in the cached statistics. To minimize skew, + <code class="varname">stats_fetch_consistency</code> can be set to + <code class="literal">snapshot</code>, at the price of increased memory usage for + caching not-needed statistics data. Conversely, if it's known that + statistics are only accessed once, caching accessed statistics is + unnecessary and can be avoided by setting + <code class="varname">stats_fetch_consistency</code> to <code class="literal">none</code>. + + You can invoke <code class="function">pg_stat_clear_snapshot</code>() to discard the + current transaction's statistics snapshot or cached values (if any). The + next use of statistical information will (when in snapshot mode) cause a + new snapshot to be built or (when in cache mode) accessed statistics to be + cached. + </p><p> + A transaction can also see its own statistics (not yet flushed out to the + shared memory statistics) in the views + <code class="structname">pg_stat_xact_all_tables</code>, + <code class="structname">pg_stat_xact_sys_tables</code>, + <code class="structname">pg_stat_xact_user_tables</code>, and + <code class="structname">pg_stat_xact_user_functions</code>. These numbers do not act as + stated above; instead they update continuously throughout the transaction. + </p><p> + 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. + Ordinary users can only see all the information about their own sessions + (sessions belonging to a role that they are a member of). In rows about + other sessions, many columns will be null. Note, however, that the + existence of a session and its general properties such as its sessions user + and database are visible to all users. Superusers and roles with privileges of + 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. + </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> + <code class="structname">pg_stat_activity</code> + <a id="id-1.6.15.7.6.7.2.2.1.1.2" class="indexterm"></a> + </td><td> + One row per server process, showing information related to + the current activity of that process, such as state and current query. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW" title="28.2.3. pg_stat_activity"> + <code class="structname">pg_stat_activity</code></a> for details. + </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 about + replication to that sender's connected standby server. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-VIEW" title="28.2.4. pg_stat_replication"> + <code class="structname">pg_stat_replication</code></a> for details. + </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 from + that receiver's connected server. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-WAL-RECEIVER-VIEW" title="28.2.6. pg_stat_wal_receiver"> + <code class="structname">pg_stat_wal_receiver</code></a> for details. + </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. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-RECOVERY-PREFETCH" title="28.2.7. pg_stat_recovery_prefetch"> + <code class="structname">pg_stat_recovery_prefetch</code></a> for details. + </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 about + the subscription workers. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION" title="28.2.8. pg_stat_subscription"> + <code class="structname">pg_stat_subscription</code></a> for details. + </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 about + SSL used on this connection. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SSL-VIEW" title="28.2.10. pg_stat_ssl"> + <code class="structname">pg_stat_ssl</code></a> for details. + </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 about + GSSAPI authentication and encryption used on this connection. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-GSSAPI-VIEW" title="28.2.11. pg_stat_gssapi"> + <code class="structname">pg_stat_gssapi</code></a> for details. + </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) running + <code class="command">ANALYZE</code>, showing current progress. + See <a class="xref" href="progress-reporting.html#ANALYZE-PROGRESS-REPORTING" title="28.4.1. ANALYZE Progress Reporting">Section 28.4.1</a>. + </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>, showing + current progress. + See <a class="xref" href="progress-reporting.html#CREATE-INDEX-PROGRESS-REPORTING" title="28.4.2. CREATE INDEX Progress Reporting">Section 28.4.2</a>. + </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) running + <code class="command">VACUUM</code>, showing current progress. + See <a class="xref" href="progress-reporting.html#VACUUM-PROGRESS-REPORTING" title="28.4.3. VACUUM Progress Reporting">Section 28.4.3</a>. + </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 running + <code class="command">CLUSTER</code> or <code class="command">VACUUM FULL</code>, showing current progress. + See <a class="xref" href="progress-reporting.html#CLUSTER-PROGRESS-REPORTING" title="28.4.4. CLUSTER Progress Reporting">Section 28.4.4</a>. + </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, + showing current progress. + See <a class="xref" href="progress-reporting.html#BASEBACKUP-PROGRESS-REPORTING" title="28.4.5. Base Backup Progress Reporting">Section 28.4.5</a>. + </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. + See <a class="xref" href="progress-reporting.html#COPY-PROGRESS-REPORTING" title="28.4.6. COPY Progress Reporting">Section 28.4.6</a>. + </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 the + WAL archiver process's activity. See + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ARCHIVER-VIEW" title="28.2.12. pg_stat_archiver"> + <code class="structname">pg_stat_archiver</code></a> for details. + </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 the + background writer process's activity. See + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-BGWRITER-VIEW" title="28.2.13. pg_stat_bgwriter"> + <code class="structname">pg_stat_bgwriter</code></a> for details. + </td></tr><tr><td><code class="structname">pg_stat_wal</code><a id="id-1.6.15.7.6.8.2.2.3.1.2" class="indexterm"></a></td><td>One row only, showing statistics about WAL activity. See + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW" title="28.2.14. pg_stat_wal"> + <code class="structname">pg_stat_wal</code></a> for details. + </td></tr><tr><td><code class="structname">pg_stat_database</code><a id="id-1.6.15.7.6.8.2.2.4.1.2" class="indexterm"></a></td><td>One row per database, showing database-wide statistics. See + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-VIEW" title="28.2.15. pg_stat_database"> + <code class="structname">pg_stat_database</code></a> for details. + </td></tr><tr><td><code class="structname">pg_stat_database_conflicts</code><a id="id-1.6.15.7.6.8.2.2.5.1.2" class="indexterm"></a></td><td> + One row per database, showing database-wide statistics about + query cancels due to conflict with recovery on standby servers. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW" title="28.2.16. pg_stat_database_conflicts"> + <code class="structname">pg_stat_database_conflicts</code></a> for details. + </td></tr><tr><td><code class="structname">pg_stat_all_tables</code><a id="id-1.6.15.7.6.8.2.2.6.1.2" class="indexterm"></a></td><td> + One row for each table in the current database, showing statistics + about accesses to that specific table. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ALL-TABLES-VIEW" title="28.2.17. pg_stat_all_tables"> + <code class="structname">pg_stat_all_tables</code></a> for details. + </td></tr><tr><td><code class="structname">pg_stat_sys_tables</code><a id="id-1.6.15.7.6.8.2.2.7.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_tables</code>, except that only + system tables are shown.</td></tr><tr><td><code class="structname">pg_stat_user_tables</code><a id="id-1.6.15.7.6.8.2.2.8.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_tables</code>, except that only user + tables are shown.</td></tr><tr><td><code class="structname">pg_stat_xact_all_tables</code><a id="id-1.6.15.7.6.8.2.2.9.1.2" class="indexterm"></a></td><td>Similar to <code class="structname">pg_stat_all_tables</code>, but counts actions + taken so far within the current transaction (which are <span class="emphasis"><em>not</em></span> + yet included in <code class="structname">pg_stat_all_tables</code> and related views). + The columns for numbers of live and dead rows and vacuum and + analyze actions are not present in this view.</td></tr><tr><td><code class="structname">pg_stat_xact_sys_tables</code><a id="id-1.6.15.7.6.8.2.2.10.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_xact_all_tables</code>, except that only + system tables are shown.</td></tr><tr><td><code class="structname">pg_stat_xact_user_tables</code><a id="id-1.6.15.7.6.8.2.2.11.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_xact_all_tables</code>, except that only + user tables are shown.</td></tr><tr><td><code class="structname">pg_stat_all_indexes</code><a id="id-1.6.15.7.6.8.2.2.12.1.2" class="indexterm"></a></td><td> + One row for each index in the current database, showing statistics + about accesses to that specific index. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ALL-INDEXES-VIEW" title="28.2.18. pg_stat_all_indexes"> + <code class="structname">pg_stat_all_indexes</code></a> for details. + </td></tr><tr><td><code class="structname">pg_stat_sys_indexes</code><a id="id-1.6.15.7.6.8.2.2.13.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_indexes</code>, except that only + indexes on system tables are shown.</td></tr><tr><td><code class="structname">pg_stat_user_indexes</code><a id="id-1.6.15.7.6.8.2.2.14.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_indexes</code>, except that only + indexes on user tables are shown.</td></tr><tr><td><code class="structname">pg_statio_all_tables</code><a id="id-1.6.15.7.6.8.2.2.15.1.2" class="indexterm"></a></td><td> + One row for each table in the current database, showing statistics + about I/O on that specific table. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-TABLES-VIEW" title="28.2.19. pg_statio_all_tables"> + <code class="structname">pg_statio_all_tables</code></a> for details. + </td></tr><tr><td><code class="structname">pg_statio_sys_tables</code><a id="id-1.6.15.7.6.8.2.2.16.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_tables</code>, except that only + system tables are shown.</td></tr><tr><td><code class="structname">pg_statio_user_tables</code><a id="id-1.6.15.7.6.8.2.2.17.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_tables</code>, except that only + user tables are shown.</td></tr><tr><td><code class="structname">pg_statio_all_indexes</code><a id="id-1.6.15.7.6.8.2.2.18.1.2" class="indexterm"></a></td><td> + One row for each index in the current database, + showing statistics about I/O on that specific index. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-INDEXES-VIEW" title="28.2.20. pg_statio_all_indexes"> + <code class="structname">pg_statio_all_indexes</code></a> for details. + </td></tr><tr><td><code class="structname">pg_statio_sys_indexes</code><a id="id-1.6.15.7.6.8.2.2.19.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_indexes</code>, except that only + indexes on system tables are shown.</td></tr><tr><td><code class="structname">pg_statio_user_indexes</code><a id="id-1.6.15.7.6.8.2.2.20.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_indexes</code>, except that only + indexes on user tables are shown.</td></tr><tr><td><code class="structname">pg_statio_all_sequences</code><a id="id-1.6.15.7.6.8.2.2.21.1.2" class="indexterm"></a></td><td> + One row for each sequence in the current database, + showing statistics about I/O on that specific sequence. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-SEQUENCES-VIEW" title="28.2.21. pg_statio_all_sequences"> + <code class="structname">pg_statio_all_sequences</code></a> for details. + </td></tr><tr><td><code class="structname">pg_statio_sys_sequences</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_sequences</code>, except that only + system sequences are shown. (Presently, no system sequences are defined, + so this view is always empty.)</td></tr><tr><td><code class="structname">pg_statio_user_sequences</code><a id="id-1.6.15.7.6.8.2.2.23.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_sequences</code>, except that only + user sequences are shown.</td></tr><tr><td><code class="structname">pg_stat_user_functions</code><a id="id-1.6.15.7.6.8.2.2.24.1.2" class="indexterm"></a></td><td> + One row for each tracked function, showing statistics + about executions of that function. See + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-USER-FUNCTIONS-VIEW" title="28.2.22. pg_stat_user_functions"> + <code class="structname">pg_stat_user_functions</code></a> for details. + </td></tr><tr><td><code class="structname">pg_stat_xact_user_functions</code><a id="id-1.6.15.7.6.8.2.2.25.1.2" class="indexterm"></a></td><td>Similar to <code class="structname">pg_stat_user_functions</code>, but counts only + calls during the current transaction (which are <span class="emphasis"><em>not</em></span> + yet included in <code class="structname">pg_stat_user_functions</code>).</td></tr><tr><td><code class="structname">pg_stat_slru</code><a id="id-1.6.15.7.6.8.2.2.26.1.2" class="indexterm"></a></td><td>One row per SLRU, showing statistics of operations. See + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SLRU-VIEW" title="28.2.23. pg_stat_slru"> + <code class="structname">pg_stat_slru</code></a> for details. + </td></tr><tr><td><code class="structname">pg_stat_replication_slots</code><a id="id-1.6.15.7.6.8.2.2.27.1.2" class="indexterm"></a></td><td>One row per replication slot, showing statistics about the + replication slot's usage. See + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW" title="28.2.5. pg_stat_replication_slots"> + <code class="structname">pg_stat_replication_slots</code></a> for details. + </td></tr><tr><td><code class="structname">pg_stat_subscription_stats</code><a id="id-1.6.15.7.6.8.2.2.28.1.2" class="indexterm"></a></td><td>One row per subscription, showing statistics about errors. + See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION-STATS" title="28.2.9. pg_stat_subscription_stats"> + <code class="structname">pg_stat_subscription_stats</code></a> for details. + </td></tr></tbody></table></div></div><br class="table-break" /><p> + The per-index statistics are particularly useful to determine which + indexes are being used and how effective they are. + </p><p> + The <code class="structname">pg_statio_</code> views are primarily useful to + determine the effectiveness of the buffer cache. When the number + of actual disk reads is much smaller than the number of buffer + hits, then the cache is satisfying most read requests without + invoking a kernel call. However, these statistics do not give the + entire story: due to the way in which <span class="productname">PostgreSQL</span> + handles disk I/O, data that is not in the + <span class="productname">PostgreSQL</span> buffer cache might still reside in the + kernel's I/O cache, and might therefore still be fetched without + requiring a physical read. Users interested in obtaining more + detailed information on <span class="productname">PostgreSQL</span> I/O behavior are + advised to use the <span class="productname">PostgreSQL</span> statistics views + in combination with operating system utilities that allow insight + into the kernel's handling of I/O. + </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></h3></div></div></div><a id="id-1.6.15.7.7.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_activity</code> view will have one row + per server process, showing information related to + the current activity of that process. + </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"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">datid</code> <code class="type">oid</code> + </p> + <p> + OID of the database this backend is connected to + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">datname</code> <code class="type">name</code> + </p> + <p> + Name of the database this backend is connected to + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">pid</code> <code class="type">integer</code> + </p> + <p> + Process ID of this backend + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">leader_pid</code> <code class="type">integer</code> + </p> + <p> + Process ID of the parallel group leader, if this process is a + parallel query worker. <code class="literal">NULL</code> if this process is a + parallel group leader or does not participate in parallel query. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">usesysid</code> <code class="type">oid</code> + </p> + <p> + OID of the user logged into this backend + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">usename</code> <code class="type">name</code> + </p> + <p> + Name of the user logged into this backend + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">application_name</code> <code class="type">text</code> + </p> + <p> + Name of the application that is connected + to this backend + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">client_addr</code> <code class="type">inet</code> + </p> + <p> + IP address of the client connected to this backend. + If this field is null, it indicates either that the client is + connected via a Unix socket on the server machine or that this is an + internal process such as autovacuum. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">client_hostname</code> <code class="type">text</code> + </p> + <p> + Host name of the connected client, as reported by a + reverse DNS lookup of <code class="structfield">client_addr</code>. This field will + 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. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">client_port</code> <code class="type">integer</code> + </p> + <p> + TCP port number that the client is using for communication + with this backend, or <code class="literal">-1</code> if a Unix socket is used. + If this field is null, it indicates that this is an internal server process. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">backend_start</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time when this process was started. For client backends, + this is the time the client connected to the server. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">xact_start</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time when this process' current transaction was started, or null + if no transaction is active. If the current + query is the first of its transaction, this column is equal to the + <code class="structfield">query_start</code> column. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">query_start</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time when the currently active query was started, or if + <code class="structfield">state</code> is not <code class="literal">active</code>, when the last query + was started + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">state_change</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time when the <code class="structfield">state</code> was last changed + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wait_event_type</code> <code class="type">text</code> + </p> + <p> + The type of event for which the backend is waiting, if any; + otherwise NULL. See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TABLE" title="Table 28.4. Wait Event Types">Table 28.4</a>. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wait_event</code> <code class="type">text</code> + </p> + <p> + Wait event name if backend is currently waiting, otherwise NULL. + 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> through + <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TIMEOUT-TABLE" title="Table 28.13. Wait Events of Type Timeout">Table 28.13</a>. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">state</code> <code class="type">text</code> + </p> + <p> + Current overall state of this backend. + Possible values are: + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + <code class="literal">active</code>: The backend is executing a query. + </p></li><li class="listitem"><p> + <code class="literal">idle</code>: The backend is waiting for a new client command. + </p></li><li class="listitem"><p> + <code class="literal">idle in transaction</code>: The backend is in a transaction, + but is not currently executing a query. + </p></li><li class="listitem"><p> + <code class="literal">idle in transaction (aborted)</code>: This state is similar to + <code class="literal">idle in transaction</code>, except one of the statements in + the transaction caused an error. + </p></li><li class="listitem"><p> + <code class="literal">fastpath function call</code>: The backend is executing a + fast-path function. + </p></li><li class="listitem"><p> + <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. + </p></li></ul></div><p> + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">backend_xid</code> <code class="type">xid</code> + </p> + <p> + Top-level transaction identifier of this backend, if any. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">backend_xmin</code> <code class="type">xid</code> + </p> + <p> + The current backend's <code class="literal">xmin</code> horizon. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">query_id</code> <code class="type">bigint</code> + </p> + <p> + Identifier of this backend's most recent query. If + <code class="structfield">state</code> is <code class="literal">active</code> this + field shows the identifier of the currently executing query. In + all other states, it shows the identifier of last query that was + executed. Query identifiers are not computed by default so this + field will be null unless <a class="xref" href="runtime-config-statistics.html#GUC-COMPUTE-QUERY-ID">compute_query_id</a> + parameter is enabled or a third-party module that computes query + identifiers is configured. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">query</code> <code class="type">text</code> + </p> + <p> + Text of this backend's most recent query. If + <code class="structfield">state</code> is <code class="literal">active</code> this field shows the + currently executing query. In all other states, it shows the last query + that was executed. By default the query text is truncated at 1024 + bytes; this value can be changed via the parameter + <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-ACTIVITY-QUERY-SIZE">track_activity_query_size</a>. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">backend_type</code> <code class="type">text</code> + </p> + <p> + Type of current backend. Possible types are + <code class="literal">autovacuum launcher</code>, <code class="literal">autovacuum worker</code>, + <code class="literal">logical replication launcher</code>, + <code class="literal">logical replication worker</code>, + <code class="literal">parallel worker</code>, <code class="literal">background writer</code>, + <code class="literal">client backend</code>, <code class="literal">checkpointer</code>, + <code class="literal">archiver</code>, + <code class="literal">startup</code>, <code class="literal">walreceiver</code>, + <code class="literal">walsender</code> and <code class="literal">walwriter</code>. + In addition, background workers registered by extensions may have + additional types. + </p></td></tr></tbody></table></div></div><br class="table-break" /><div class="note"><h3 class="title">Note</h3><p> + The <code class="structfield">wait_event</code> and <code class="structfield">state</code> columns are + independent. If a backend is in the <code class="literal">active</code> state, + it may or may not be <code class="literal">waiting</code> on some event. If the state + is <code class="literal">active</code> and <code class="structfield">wait_event</code> is non-null, it + means that a query is being executed, but is being blocked somewhere + in the system. + </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 process + waiting for activity in its main processing loop. + <code class="literal">wait_event</code> will identify the specific wait point; + 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>. + </td></tr><tr><td><code class="literal">BufferPin</code></td><td>The server process is waiting for exclusive access to + a data buffer. Buffer pin waits can be protracted if + another process holds an open cursor that last read data from the + 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>. + </td></tr><tr><td><code class="literal">Client</code></td><td>The server process is waiting for activity on a socket + connected to a user application. Thus, the server expects something + to happen that is independent of its internal processes. + <code class="literal">wait_event</code> will identify the specific wait point; + 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>. + </td></tr><tr><td><code class="literal">Extension</code></td><td>The server process is waiting for some condition defined by an + extension module. + 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>. + </td></tr><tr><td><code class="literal">IO</code></td><td>The server process is waiting for an I/O operation to complete. + <code class="literal">wait_event</code> will identify the specific wait point; + 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>. + </td></tr><tr><td><code class="literal">IPC</code></td><td>The server process is waiting for some interaction with + another server process. <code class="literal">wait_event</code> will + identify the specific wait point; + 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>. + </td></tr><tr><td><code class="literal">Lock</code></td><td>The server process is waiting for a heavyweight lock. + Heavyweight locks, also known as lock manager locks or simply locks, + primarily protect SQL-visible objects such as tables. However, + they are also used to ensure mutual exclusion for certain internal + operations such as relation extension. <code class="literal">wait_event</code> + will identify the type of lock awaited; + 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>. + </td></tr><tr><td><code class="literal">LWLock</code></td><td> The server process is waiting for a lightweight lock. + Most such locks protect a particular data structure in shared memory. + <code class="literal">wait_event</code> will contain a name identifying the purpose + of the lightweight lock. (Some locks have specific names; others + are part of a group of locks each with a similar purpose.) + 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>. + </td></tr><tr><td><code class="literal">Timeout</code></td><td>The server process is waiting for a timeout + to expire. <code class="literal">wait_event</code> will identify the specific wait + 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>. + </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">RecoveryWalStream</code></td><td>Waiting in main loop of startup process for WAL to arrive, during + 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 GSSAPI + session.</td></tr><tr><td><code class="literal">LibPQWalReceiverConnect</code></td><td>Waiting in WAL receiver to establish connection to remote + 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 WAL + 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">BufFileWrite</code></td><td>Waiting for a write to 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">ControlFileRead</code></td><td>Waiting for a read from the <code class="filename">pg_control</code> + file.</td></tr><tr><td><code class="literal">ControlFileSync</code></td><td>Waiting for the <code class="filename">pg_control</code> file to reach + 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> file + 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> + 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> + 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">DSMFillZeroWrite</code></td><td>Waiting to fill a dynamic shared memory backing file with + 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 to + durable storage.</td></tr><tr><td><code class="literal">DataFilePrefetch</code></td><td>Waiting for an asynchronous prefetch from a relation data + 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 lock + file.</td></tr><tr><td><code class="literal">LockFileAddToDataDirSync</code></td><td>Waiting for data to reach durable storage while adding a line to the + 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 directory + lock file.</td></tr><tr><td><code class="literal">LockFileCreateRead</code></td><td>Waiting to read while creating the data directory lock + file.</td></tr><tr><td><code class="literal">LockFileCreateSync</code></td><td>Waiting for data to reach durable storage while creating the data + directory lock file.</td></tr><tr><td><code class="literal">LockFileCreateWrite</code></td><td>Waiting for a write while creating the data directory lock + file.</td></tr><tr><td><code class="literal">LockFileReCheckDataDirRead</code></td><td>Waiting for a read during recheck of the data directory lock + file.</td></tr><tr><td><code class="literal">LogicalRewriteCheckpointSync</code></td><td>Waiting for logical rewrite mappings to reach durable storage + during a checkpoint.</td></tr><tr><td><code class="literal">LogicalRewriteMappingSync</code></td><td>Waiting for mapping data to reach durable storage during a logical + rewrite.</td></tr><tr><td><code class="literal">LogicalRewriteMappingWrite</code></td><td>Waiting for a write of mapping data during a logical + rewrite.</td></tr><tr><td><code class="literal">LogicalRewriteSync</code></td><td>Waiting for logical rewrite mappings to reach durable + storage.</td></tr><tr><td><code class="literal">LogicalRewriteTruncate</code></td><td>Waiting for truncate of mapping data during a logical + 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">RelationMapSync</code></td><td>Waiting for the relation map file to reach durable storage.</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 buffer + 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 storage + 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 durable + 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 checkpoint + 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 page + 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 catalog + snapshot.</td></tr><tr><td><code class="literal">SnapbuildSync</code></td><td>Waiting for a serialized historical catalog snapshot to reach + durable storage.</td></tr><tr><td><code class="literal">SnapbuildWrite</code></td><td>Waiting for a write of a serialized historical catalog + snapshot.</td></tr><tr><td><code class="literal">TimelineHistoryFileSync</code></td><td>Waiting for a timeline history file received via streaming + 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 via + 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 durable + storage.</td></tr><tr><td><code class="literal">TimelineHistoryWrite</code></td><td>Waiting for a write of a newly created timeline history + 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">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 during + 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 an + 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 to + 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 an + existing one.</td></tr><tr><td><code class="literal">WALInitSync</code></td><td>Waiting for a newly initialized WAL file to reach durable + 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 walsender + 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 new + 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> plan + 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> to + 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> to + 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 successfully + 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-tree + 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 while + 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 hash + table.</td></tr><tr><td><code class="literal">HashBatchElect</code></td><td>Waiting to elect a Parallel Hash participant to allocate a hash + table.</td></tr><tr><td><code class="literal">HashBatchLoad</code></td><td>Waiting for other Parallel Hash participants to finish loading a + hash table.</td></tr><tr><td><code class="literal">HashBuildAllocate</code></td><td>Waiting for an elected Parallel Hash participant to allocate the + initial hash table.</td></tr><tr><td><code class="literal">HashBuildElect</code></td><td>Waiting to elect a Parallel Hash participant to allocate the + initial hash table.</td></tr><tr><td><code class="literal">HashBuildHashInner</code></td><td>Waiting for other Parallel Hash participants to finish hashing the + inner relation.</td></tr><tr><td><code class="literal">HashBuildHashOuter</code></td><td>Waiting for other Parallel Hash participants to finish partitioning + the outer relation.</td></tr><tr><td><code class="literal">HashGrowBatchesAllocate</code></td><td>Waiting for an elected Parallel Hash participant to allocate more + batches.</td></tr><tr><td><code class="literal">HashGrowBatchesDecide</code></td><td>Waiting to elect a Parallel Hash participant to decide on future + batch growth.</td></tr><tr><td><code class="literal">HashGrowBatchesElect</code></td><td>Waiting to elect a Parallel Hash participant to allocate more + batches.</td></tr><tr><td><code class="literal">HashGrowBatchesFinish</code></td><td>Waiting for an elected Parallel Hash participant to decide on + future batch growth.</td></tr><tr><td><code class="literal">HashGrowBatchesRepartition</code></td><td>Waiting for other Parallel Hash participants to finish + repartitioning.</td></tr><tr><td><code class="literal">HashGrowBucketsAllocate</code></td><td>Waiting for an elected Parallel Hash participant to finish + allocating more buckets.</td></tr><tr><td><code class="literal">HashGrowBucketsElect</code></td><td>Waiting to elect a Parallel Hash participant to allocate more + buckets.</td></tr><tr><td><code class="literal">HashGrowBucketsReinsert</code></td><td>Waiting for other Parallel Hash participants to finish inserting + tuples into new buckets.</td></tr><tr><td><code class="literal">LogicalSyncData</code></td><td>Waiting for a logical replication remote server to send data for + initial table synchronization.</td></tr><tr><td><code class="literal">LogicalSyncStateChange</code></td><td>Waiting for a logical replication remote server to change + state.</td></tr><tr><td><code class="literal">MessageQueueInternal</code></td><td>Waiting for another process to be attached to a shared message + 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 to + 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 at + 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 all + 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 vacuum + cleanup.</td></tr><tr><td><code class="literal">RecoveryConflictTablespace</code></td><td>Waiting for recovery conflict resolution for dropping a + 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> to + 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 be + dropped.</td></tr><tr><td><code class="literal">ReplicationSlotDrop</code></td><td>Waiting for a replication slot to become inactive so it can be + 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> to + complete.</td></tr><tr><td><code class="literal">SafeSnapshot</code></td><td>Waiting to obtain a valid snapshot for a <code class="literal">READ ONLY + DEFERRABLE</code> transaction.</td></tr><tr><td><code class="literal">SyncRep</code></td><td>Waiting for confirmation from a remote server during synchronous + 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 streaming + replication.</td></tr><tr><td><code class="literal">XactGroupUpdate</code></td><td>Waiting for the group leader to update transaction status at + 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">extend</code></td><td>Waiting to extend a relation.</td></tr><tr><td><code class="literal">frozenid</code></td><td>Waiting to + update <code class="structname">pg_database</code>.<code class="structfield">datfrozenxid</code> + 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.</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 shared + memory.</td></tr><tr><td><code class="literal">AutoFile</code></td><td>Waiting to update the <code class="filename">postgresql.auto.conf</code> + file.</td></tr><tr><td><code class="literal">Autovacuum</code></td><td>Waiting to read or update the current state of autovacuum + workers.</td></tr><tr><td><code class="literal">AutovacuumSchedule</code></td><td>Waiting to ensure that a table selected for autovacuum + 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 a + 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 buffer + 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 a + 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> + 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 allocation + information.</td></tr><tr><td><code class="literal">LockFastPath</code></td><td>Waiting to read or update a process' fast-path lock + information.</td></tr><tr><td><code class="literal">LockManager</code></td><td>Waiting to read or update information + about <span class="quote">“<span class="quote">heavyweight</span>”</span> locks.</td></tr><tr><td><code class="literal">LogicalRepWorker</code></td><td>Waiting to read or update the state of logical replication + 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 SLRU + 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> message + storage.</td></tr><tr><td><code class="literal">NotifySLRU</code></td><td>Waiting to access the <code class="command">NOTIFY</code> message SLRU + 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 plan + execution.</td></tr><tr><td><code class="literal">ParallelHashJoin</code></td><td>Waiting to synchronize workers during Parallel Hash Join plan + 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 composite + types.</td></tr><tr><td><code class="literal">PerSessionRecordTypmod</code></td><td>Waiting to access a parallel query's information about type + 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 current + serializable transaction during a parallel query.</td></tr><tr><td><code class="literal">PredicateLockManager</code></td><td>Waiting to access predicate lock information used by + serializable transactions.</td></tr><tr><td><code class="literal">ProcArray</code></td><td>Waiting to access the shared per-process data structures + (typically, to get a snapshot or report a session's transaction + ID).</td></tr><tr><td><code class="literal">RelationMapping</code></td><td>Waiting to read or update + a <code class="filename">pg_filenode.map</code> file (used to track the + 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> + 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 replication + 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 SLRU + buffer.</td></tr><tr><td><code class="literal">SerializableFinishedList</code></td><td>Waiting to access the list of finished serializable + transactions.</td></tr><tr><td><code class="literal">SerializablePredicateList</code></td><td>Waiting to access the list of predicate locks held by + serializable transactions.</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">PgStatsData</code></td><td>Waiting for shared memory stats data access</td></tr><tr><td><code class="literal">SerializableXactHash</code></td><td>Waiting to read or update information about serializable + transactions.</td></tr><tr><td><code class="literal">SerialSLRU</code></td><td>Waiting to access the serializable transaction conflict SLRU + cache.</td></tr><tr><td><code class="literal">SharedTidBitmap</code></td><td>Waiting to access a shared TID bitmap during a parallel bitmap + index scan.</td></tr><tr><td><code class="literal">SharedTupleStore</code></td><td>Waiting to access a shared tuple store during parallel + 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 invalidation + queue.</td></tr><tr><td><code class="literal">SInvalWrite</code></td><td>Waiting to add a message to the shared catalog invalidation + 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 of + synchronous replication.</td></tr><tr><td><code class="literal">SyncScan</code></td><td>Waiting to select the starting location of a synchronized table + 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 multixact + 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 update + 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> + Extensions can add <code class="literal">LWLock</code> types to the list shown in + <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 name + assigned by an extension will not be available in all server processes; + so an <code class="literal">LWLock</code> wait event might be reported as + just <span class="quote">“<span class="quote"><code class="literal">extension</code></span>”</span> rather than the + extension-assigned name. + </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> or + a sibling function.</td></tr><tr><td><code class="literal">RecoveryApplyDelay</code></td><td>Waiting to apply WAL during recovery because of a delay + setting.</td></tr><tr><td><code class="literal">RecoveryRetrieveRetryInterval</code></td><td>Waiting during recovery when WAL data is not available from any + 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 the + checkpointer, because the request queue is full.</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 any + empty pages at the end of a table vacuumed.</td></tr></tbody></table></div></div><br class="table-break" /><p> + Here is an example of how wait events can be viewed: + +</p><pre class="programlisting"> +SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event is NOT NULL; + pid | wait_event_type | wait_event +------+-----------------+------------ + 2540 | Lock | relation + 6644 | LWLock | ProcArray +(2 rows) +</pre><p> + </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></h3></div></div></div><a id="id-1.6.15.7.8.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_replication</code> view will contain one row + per WAL sender process, showing statistics about replication to that + sender's connected standby server. Only directly connected standbys are + listed; no information is available about downstream standby servers. + </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"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">pid</code> <code class="type">integer</code> + </p> + <p> + Process ID of a WAL sender process + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">usesysid</code> <code class="type">oid</code> + </p> + <p> + OID of the user logged into this WAL sender process + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">usename</code> <code class="type">name</code> + </p> + <p> + Name of the user logged into this WAL sender process + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">application_name</code> <code class="type">text</code> + </p> + <p> + Name of the application that is connected + to this WAL sender + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">client_addr</code> <code class="type">inet</code> + </p> + <p> + IP address of the client connected to this WAL sender. + If this field is null, it indicates that the client is + connected via a Unix socket on the server machine. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">client_hostname</code> <code class="type">text</code> + </p> + <p> + Host name of the connected client, as reported by a + reverse DNS lookup of <code class="structfield">client_addr</code>. This field will + 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. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">client_port</code> <code class="type">integer</code> + </p> + <p> + TCP port number that the client is using for communication + with this WAL sender, or <code class="literal">-1</code> if a Unix socket is used + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">backend_start</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time when this process was started, i.e., when the + client connected to this WAL sender + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">backend_xmin</code> <code class="type">xid</code> + </p> + <p> + This standby's <code class="literal">xmin</code> horizon reported + by <a class="xref" href="runtime-config-replication.html#GUC-HOT-STANDBY-FEEDBACK">hot_standby_feedback</a>. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">state</code> <code class="type">text</code> + </p> + <p> + Current WAL sender state. + Possible values are: + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + <code class="literal">startup</code>: This WAL sender is starting up. + </p></li><li class="listitem"><p> + <code class="literal">catchup</code>: This WAL sender's connected standby is + catching up with the primary. + </p></li><li class="listitem"><p> + <code class="literal">streaming</code>: This WAL sender is streaming changes + after its connected standby server has caught up with the primary. + </p></li><li class="listitem"><p> + <code class="literal">backup</code>: This WAL sender is sending a backup. + </p></li><li class="listitem"><p> + <code class="literal">stopping</code>: This WAL sender is stopping. + </p></li></ul></div><p> + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sent_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + Last write-ahead log location sent on this connection + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">write_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + Last write-ahead log location written to disk by this standby + server + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">flush_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + Last write-ahead log location flushed to disk by this standby + server + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">replay_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + Last write-ahead log location replayed into the database on this + standby server + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">write_lag</code> <code class="type">interval</code> + </p> + <p> + Time elapsed between flushing recent WAL locally and receiving + notification that this standby server has written it (but not yet + flushed it or applied it). This can be used to gauge the delay that + <code class="literal">synchronous_commit</code> level + <code class="literal">remote_write</code> incurred while committing if this + server was configured as a synchronous standby. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">flush_lag</code> <code class="type">interval</code> + </p> + <p> + Time elapsed between flushing recent WAL locally and receiving + notification that this standby server has written and flushed it + (but not yet applied it). This can be used to gauge the delay that + <code class="literal">synchronous_commit</code> level + <code class="literal">on</code> incurred while committing if this + server was configured as a synchronous standby. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">replay_lag</code> <code class="type">interval</code> + </p> + <p> + Time elapsed between flushing recent WAL locally and receiving + notification that this standby server has written, flushed and + applied it. This can be used to gauge the delay that + <code class="literal">synchronous_commit</code> level + <code class="literal">remote_apply</code> incurred while committing if this + server was configured as a synchronous standby. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sync_priority</code> <code class="type">integer</code> + </p> + <p> + Priority of this standby server for being chosen as the + synchronous standby in a priority-based synchronous replication. + This has no effect in a quorum-based synchronous replication. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sync_state</code> <code class="type">text</code> + </p> + <p> + Synchronous state of this standby server. + Possible values are: + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + <code class="literal">async</code>: This standby server is asynchronous. + </p></li><li class="listitem"><p> + <code class="literal">potential</code>: This standby server is now asynchronous, + but can potentially become synchronous if one of current + synchronous ones fails. + </p></li><li class="listitem"><p> + <code class="literal">sync</code>: This standby server is synchronous. + </p></li><li class="listitem"><p> + <code class="literal">quorum</code>: This standby server is considered as a candidate + for quorum standbys. + </p></li></ul></div><p> + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">reply_time</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Send time of last reply message received from standby server + </p></td></tr></tbody></table></div></div><br class="table-break" /><p> + The lag times reported in the <code class="structname">pg_stat_replication</code> + view are measurements of the time taken for recent WAL to be written, + flushed and replayed and for the sender to know about it. These times + represent the commit delay that was (or would have been) introduced by each + synchronous commit level, if the remote server was configured as a + synchronous standby. For an asynchronous standby, the + <code class="structfield">replay_lag</code> column approximates the delay + before recent transactions became visible to queries. If the standby + server has entirely caught up with the sending server and there is no more + WAL activity, the most recently measured lag times will continue to be + displayed for a short time and then show NULL. + </p><p> + Lag times work automatically for physical replication. Logical decoding + plugins may optionally emit tracking messages; if they do not, the tracking + mechanism will simply display NULL lag. + </p><div class="note"><h3 class="title">Note</h3><p> + The reported lag times are not predictions of how long it will take for + the standby to catch up with the sending server assuming the current + rate of replay. Such a system would show similar times while new WAL is + being generated, but would differ when the sender becomes idle. In + particular, when the standby has caught up completely, + <code class="structname">pg_stat_replication</code> shows the time taken to + write, flush and replay the most recent reported WAL location rather than + zero as some users might expect. This is consistent with the goal of + measuring synchronous commit and transaction visibility delays for + recent write transactions. + To reduce confusion for users expecting a different model of lag, the + lag columns revert to NULL after a short time on a fully replayed idle + system. Monitoring systems should choose whether to represent this + as missing data, zero or continue to display the last known value. + </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></h3></div></div></div><a id="id-1.6.15.7.9.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_replication_slots</code> view will contain + one row per logical replication slot, showing statistics about its usage. + </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"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">slot_name</code> <code class="type">text</code> + </p> + <p> + A unique, cluster-wide identifier for the replication slot + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">spill_txns</code> <code class="type">bigint</code> + </p> + <p> + Number of transactions spilled to disk once the memory used by + logical decoding to decode changes from WAL has exceeded + <code class="literal">logical_decoding_work_mem</code>. The counter gets + incremented for both top-level transactions and subtransactions. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">spill_count</code> <code class="type">bigint</code> + </p> + <p> + Number of times transactions were spilled to disk while decoding + changes from WAL for this slot. This counter is incremented each time + a transaction is spilled, and the same transaction may be spilled + multiple times. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">spill_bytes</code> <code class="type">bigint</code> + </p> + <p> + Amount of decoded transaction data spilled to disk while performing + decoding of changes from WAL for this slot. This and other spill + counters can be used to gauge the I/O which occurred during logical + decoding and allow tuning <code class="literal">logical_decoding_work_mem</code>. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stream_txns</code> <code class="type">bigint</code> + </p> + <p> + Number of in-progress transactions streamed to the decoding output + plugin after the memory used by logical decoding to decode changes + from WAL for this slot has exceeded + <code class="literal">logical_decoding_work_mem</code>. Streaming only + works with top-level transactions (subtransactions can't be streamed + independently), so the counter is not incremented for subtransactions. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stream_count</code><code class="type">bigint</code> + </p> + <p> + Number of times in-progress transactions were streamed to the decoding + output plugin while decoding changes from WAL for this slot. This + counter is incremented each time a transaction is streamed, and the + same transaction may be streamed multiple times. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stream_bytes</code><code class="type">bigint</code> + </p> + <p> + Amount of transaction data decoded for streaming in-progress + transactions to the decoding output plugin while decoding changes from + WAL for this slot. This and other streaming counters for this slot can + be used to tune <code class="literal">logical_decoding_work_mem</code>. + </p> + </td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">total_txns</code> <code class="type">bigint</code> + </p> + <p> + Number of decoded transactions sent to the decoding output plugin for + this slot. This counts top-level transactions only, and is not incremented + for subtransactions. Note that this includes the transactions that are + streamed and/or spilled. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">total_bytes</code><code class="type">bigint</code> + </p> + <p> + Amount of transaction data decoded for sending transactions to the + decoding output plugin while decoding changes from WAL for this slot. + Note that this includes data that is streamed and/or spilled. + </p> + </td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time at which these statistics were last reset + </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></h3></div></div></div><a id="id-1.6.15.7.10.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_wal_receiver</code> view will contain only + one row, showing statistics about the WAL receiver from that receiver's + connected server. + </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"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">pid</code> <code class="type">integer</code> + </p> + <p> + Process ID of the WAL receiver process + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">status</code> <code class="type">text</code> + </p> + <p> + Activity status of the WAL receiver process + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">receive_start_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + First write-ahead log location used when WAL receiver is + started + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">receive_start_tli</code> <code class="type">integer</code> + </p> + <p> + First timeline number used when WAL receiver is started + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">written_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + Last write-ahead log location already received and written to disk, + but not flushed. This should not be used for data integrity checks. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">flushed_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + Last write-ahead log location already received and flushed to + disk, the initial value of this field being the first log location used + when WAL receiver is started + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">received_tli</code> <code class="type">integer</code> + </p> + <p> + Timeline number of last write-ahead log location received and + flushed to disk, the initial value of this field being the timeline + number of the first log location used when WAL receiver is started + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_msg_send_time</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Send time of last message received from origin WAL sender + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_msg_receipt_time</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Receipt time of last message received from origin WAL sender + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">latest_end_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + Last write-ahead log location reported to origin WAL sender + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">latest_end_time</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time of last write-ahead log location reported to origin WAL sender + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">slot_name</code> <code class="type">text</code> + </p> + <p> + Replication slot name used by this WAL receiver + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sender_host</code> <code class="type">text</code> + </p> + <p> + Host of the <span class="productname">PostgreSQL</span> instance + this WAL receiver is connected to. This can be a host name, + an IP address, or a directory path if the connection is via + Unix socket. (The path case can be distinguished because it + will always be an absolute path, beginning with <code class="literal">/</code>.) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sender_port</code> <code class="type">integer</code> + </p> + <p> + Port number of the <span class="productname">PostgreSQL</span> instance + this WAL receiver is connected to. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">conninfo</code> <code class="type">text</code> + </p> + <p> + Connection string used by this WAL receiver, + with security-sensitive fields obfuscated. + </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></h3></div></div></div><a id="id-1.6.15.7.11.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_recovery_prefetch</code> view will contain + only one row. The columns <code class="structfield">wal_distance</code>, + <code class="structfield">block_distance</code> and + <code class="structfield">io_depth</code> show current values, and the + other columns show cumulative counters that can be reset + with the <code class="function">pg_stat_reset_shared</code> function. + </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"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time at which these statistics were last reset + </p> + </td></tr><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">prefetch</code> <code class="type">bigint</code> + </p> + <p> + Number of blocks prefetched because they were not in the buffer pool + </p> + </td></tr><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">hit</code> <code class="type">bigint</code> + </p> + <p> + Number of blocks not prefetched because they were already in the buffer pool + </p> + </td></tr><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">skip_init</code> <code class="type">bigint</code> + </p> + <p> + Number of blocks not prefetched because they would be zero-initialized + </p> + </td></tr><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">skip_new</code> <code class="type">bigint</code> + </p> + <p> + Number of blocks not prefetched because they didn't exist yet + </p> + </td></tr><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">skip_fpw</code> <code class="type">bigint</code> + </p> + <p> + Number of blocks not prefetched because a full page image was included in the WAL + </p> + </td></tr><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">skip_rep</code> <code class="type">bigint</code> + </p> + <p> + Number of blocks not prefetched because they were already recently prefetched + </p> + </td></tr><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">wal_distance</code> <code class="type">int</code> + </p> + <p> + How many bytes ahead the prefetcher is looking + </p> + </td></tr><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">block_distance</code> <code class="type">int</code> + </p> + <p> + How many blocks ahead the prefetcher is looking + </p> + </td></tr><tr><td class="catalog_table_entry"> + <p class="column_definition"> + <code class="structfield">io_depth</code> <code class="type">int</code> + </p> + <p> + How many prefetches have been initiated but are not yet known to have completed + </p> + </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></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"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">subid</code> <code class="type">oid</code> + </p> + <p> + OID of the subscription + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">subname</code> <code class="type">name</code> + </p> + <p> + Name of the subscription + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">pid</code> <code class="type">integer</code> + </p> + <p> + Process ID of the subscription worker process + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relid</code> <code class="type">oid</code> + </p> + <p> + OID of the relation that the worker is synchronizing; null for the + main apply worker + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">received_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + Last write-ahead log location received, the initial value of + this field being 0 + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_msg_send_time</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Send time of last message received from origin WAL sender + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_msg_receipt_time</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Receipt time of last message received from origin WAL sender + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">latest_end_lsn</code> <code class="type">pg_lsn</code> + </p> + <p> + Last write-ahead log location reported to origin WAL sender + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">latest_end_time</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time of last write-ahead log location reported to origin WAL + sender + </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></h3></div></div></div><a id="id-1.6.15.7.13.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_subscription_stats</code> view will contain + one row per subscription. + </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"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">subid</code> <code class="type">oid</code> + </p> + <p> + OID of the subscription + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">subname</code> <code class="type">name</code> + </p> + <p> + Name of the subscription + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">apply_error_count</code> <code class="type">bigint</code> + </p> + <p> + Number of times an error occurred while applying changes + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sync_error_count</code> <code class="type">bigint</code> + </p> + <p> + Number of times an error occurred during the initial table + synchronization + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time at which these statistics were last reset + </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></h3></div></div></div><a id="id-1.6.15.7.14.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_ssl</code> view will contain one row per + backend or WAL sender process, showing statistics about SSL usage on + this connection. It can be joined to <code class="structname">pg_stat_activity</code> + or <code class="structname">pg_stat_replication</code> on the + <code class="structfield">pid</code> column to get more details about the + connection. + </p><div class="table" id="PG-STAT-SSL-VIEW"><p class="title"><strong>Table 28.20. <code class="structname">pg_stat_ssl</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_ssl View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">pid</code> <code class="type">integer</code> + </p> + <p> + Process ID of a backend or WAL sender process + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">ssl</code> <code class="type">boolean</code> + </p> + <p> + True if SSL is used on this connection + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">version</code> <code class="type">text</code> + </p> + <p> + Version of SSL in use, or NULL if SSL is not in use + on this connection + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">cipher</code> <code class="type">text</code> + </p> + <p> + Name of SSL cipher in use, or NULL if SSL is not in use + on this connection + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">bits</code> <code class="type">integer</code> + </p> + <p> + Number of bits in the encryption algorithm used, or NULL + if SSL is not used on this connection + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">client_dn</code> <code class="type">text</code> + </p> + <p> + Distinguished Name (DN) field from the client certificate + used, or NULL if no client certificate was supplied or if SSL + is not in use on this connection. This field is truncated if the + DN field is longer than <code class="symbol">NAMEDATALEN</code> (64 characters + in a standard build). + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">client_serial</code> <code class="type">numeric</code> + </p> + <p> + Serial number of the client certificate, or NULL if no client + certificate was supplied or if SSL is not in use on this connection. The + combination of certificate serial number and certificate issuer uniquely + identifies a certificate (unless the issuer erroneously reuses serial + numbers). + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">issuer_dn</code> <code class="type">text</code> + </p> + <p> + DN of the issuer of the client certificate, or NULL if no client + certificate was supplied or if SSL is not in use on this connection. + This field is truncated like <code class="structfield">client_dn</code>. + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-GSSAPI-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.11. <code class="structname">pg_stat_gssapi</code></h3></div></div></div><a id="id-1.6.15.7.15.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_gssapi</code> view will contain one row per + backend, showing information about GSSAPI usage on this connection. It can + be joined to <code class="structname">pg_stat_activity</code> or + <code class="structname">pg_stat_replication</code> on the + <code class="structfield">pid</code> column to get more details about the + connection. + </p><div class="table" id="PG-STAT-GSSAPI-VIEW"><p class="title"><strong>Table 28.21. <code class="structname">pg_stat_gssapi</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_gssapi View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">pid</code> <code class="type">integer</code> + </p> + <p> + Process ID of a backend + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">gss_authenticated</code> <code class="type">boolean</code> + </p> + <p> + True if GSSAPI authentication was used for this connection + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">principal</code> <code class="type">text</code> + </p> + <p> + Principal used to authenticate this connection, or NULL + if GSSAPI was not used to authenticate this connection. This + field is truncated if the principal is longer than + <code class="symbol">NAMEDATALEN</code> (64 characters in a standard build). + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">encrypted</code> <code class="type">boolean</code> + </p> + <p> + True if GSSAPI encryption is in use on this connection + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-ARCHIVER-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.12. <code class="structname">pg_stat_archiver</code></h3></div></div></div><a id="id-1.6.15.7.16.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_archiver</code> view will always have a + single row, containing data about the archiver process of the cluster. + </p><div class="table" id="PG-STAT-ARCHIVER-VIEW"><p class="title"><strong>Table 28.22. <code class="structname">pg_stat_archiver</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_archiver View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">archived_count</code> <code class="type">bigint</code> + </p> + <p> + Number of WAL files that have been successfully archived + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_archived_wal</code> <code class="type">text</code> + </p> + <p> + Name of the WAL file most recently successfully archived + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_archived_time</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time of the most recent successful archive operation + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">failed_count</code> <code class="type">bigint</code> + </p> + <p> + Number of failed attempts for archiving WAL files + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_failed_wal</code> <code class="type">text</code> + </p> + <p> + Name of the WAL file of the most recent failed archival operation + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_failed_time</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time of the most recent failed archival operation + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time at which these statistics were last reset + </p></td></tr></tbody></table></div></div><br class="table-break" /><p> + Normally, WAL files are archived in order, oldest to newest, but that is + not guaranteed, and does not hold under special circumstances like when + promoting a standby or after crash recovery. Therefore it is not safe to + assume that all files older than + <code class="structfield">last_archived_wal</code> have also been successfully + archived. + </p></div><div class="sect2" id="MONITORING-PG-STAT-BGWRITER-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.13. <code class="structname">pg_stat_bgwriter</code></h3></div></div></div><a id="id-1.6.15.7.17.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_bgwriter</code> view will always have a + single row, containing global data for the cluster. + </p><div class="table" id="PG-STAT-BGWRITER-VIEW"><p class="title"><strong>Table 28.23. <code class="structname">pg_stat_bgwriter</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_bgwriter View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">checkpoints_timed</code> <code class="type">bigint</code> + </p> + <p> + Number of scheduled checkpoints that have been performed + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">checkpoints_req</code> <code class="type">bigint</code> + </p> + <p> + Number of requested checkpoints that have been performed + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">checkpoint_write_time</code> <code class="type">double precision</code> + </p> + <p> + Total amount of time that has been spent in the portion of + checkpoint processing where files are written to disk, in milliseconds + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">checkpoint_sync_time</code> <code class="type">double precision</code> + </p> + <p> + Total amount of time that has been spent in the portion of + checkpoint processing where files are synchronized to disk, in + milliseconds + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">buffers_checkpoint</code> <code class="type">bigint</code> + </p> + <p> + Number of buffers written during checkpoints + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">buffers_clean</code> <code class="type">bigint</code> + </p> + <p> + Number of buffers written by the background writer + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">maxwritten_clean</code> <code class="type">bigint</code> + </p> + <p> + Number of times the background writer stopped a cleaning + scan because it had written too many buffers + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">buffers_backend</code> <code class="type">bigint</code> + </p> + <p> + Number of buffers written directly by a backend + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">buffers_backend_fsync</code> <code class="type">bigint</code> + </p> + <p> + Number of times a backend had to execute its own + <code class="function">fsync</code> call (normally the background writer handles those + even when the backend does its own write) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">buffers_alloc</code> <code class="type">bigint</code> + </p> + <p> + Number of buffers allocated + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time at which these statistics were last reset + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-WAL-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.14. <code class="structname">pg_stat_wal</code></h3></div></div></div><a id="id-1.6.15.7.18.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_wal</code> view will always have a + single row, containing data about WAL activity of the cluster. + </p><div class="table" id="PG-STAT-WAL-VIEW"><p class="title"><strong>Table 28.24. <code class="structname">pg_stat_wal</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_wal View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wal_records</code> <code class="type">bigint</code> + </p> + <p> + Total number of WAL records generated + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wal_fpi</code> <code class="type">bigint</code> + </p> + <p> + Total number of WAL full page images generated + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wal_bytes</code> <code class="type">numeric</code> + </p> + <p> + Total amount of WAL generated in bytes + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wal_buffers_full</code> <code class="type">bigint</code> + </p> + <p> + Number of times WAL data was written to disk because WAL buffers became full + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wal_write</code> <code class="type">bigint</code> + </p> + <p> + Number of times WAL buffers were written out to disk via + <code class="function">XLogWrite</code> request. + See <a class="xref" href="wal-configuration.html" title="30.5. WAL Configuration">Section 30.5</a> for more information about + the internal WAL function <code class="function">XLogWrite</code>. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wal_sync</code> <code class="type">bigint</code> + </p> + <p> + Number of times WAL files were synced to disk via + <code class="function">issue_xlog_fsync</code> request + (if <a class="xref" href="runtime-config-wal.html#GUC-FSYNC">fsync</a> is <code class="literal">on</code> and + <a class="xref" href="runtime-config-wal.html#GUC-WAL-SYNC-METHOD">wal_sync_method</a> is either + <code class="literal">fdatasync</code>, <code class="literal">fsync</code> or + <code class="literal">fsync_writethrough</code>, otherwise zero). + See <a class="xref" href="wal-configuration.html" title="30.5. WAL Configuration">Section 30.5</a> for more information about + the internal WAL function <code class="function">issue_xlog_fsync</code>. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wal_write_time</code> <code class="type">double precision</code> + </p> + <p> + Total amount of time spent writing WAL buffers to disk via + <code class="function">XLogWrite</code> request, in milliseconds + (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-WAL-IO-TIMING">track_wal_io_timing</a> is enabled, + otherwise zero). This includes the sync time when + <code class="varname">wal_sync_method</code> is either + <code class="literal">open_datasync</code> or <code class="literal">open_sync</code>. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">wal_sync_time</code> <code class="type">double precision</code> + </p> + <p> + Total amount of time spent syncing WAL files to disk via + <code class="function">issue_xlog_fsync</code> request, in milliseconds + (if <code class="varname">track_wal_io_timing</code> is enabled, + <code class="varname">fsync</code> is <code class="literal">on</code>, and + <code class="varname">wal_sync_method</code> is either + <code class="literal">fdatasync</code>, <code class="literal">fsync</code> or + <code class="literal">fsync_writethrough</code>, otherwise zero). + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time at which these statistics were last reset + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-DATABASE-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.15. <code class="structname">pg_stat_database</code></h3></div></div></div><a id="id-1.6.15.7.19.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_database</code> view will contain one row + for each database in the cluster, plus one for shared objects, showing + database-wide statistics. + </p><div class="table" id="PG-STAT-DATABASE-VIEW"><p class="title"><strong>Table 28.25. <code class="structname">pg_stat_database</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_database View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">datid</code> <code class="type">oid</code> + </p> + <p> + OID of this database, or 0 for objects belonging to a shared + relation + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">datname</code> <code class="type">name</code> + </p> + <p> + Name of this database, or <code class="literal">NULL</code> for shared + objects. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">numbackends</code> <code class="type">integer</code> + </p> + <p> + Number of backends currently connected to this database, or + <code class="literal">NULL</code> for shared objects. This is the only column + in this view that returns a value reflecting current state; all other + columns return the accumulated values since the last reset. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">xact_commit</code> <code class="type">bigint</code> + </p> + <p> + Number of transactions in this database that have been + committed + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">xact_rollback</code> <code class="type">bigint</code> + </p> + <p> + Number of transactions in this database that have been + rolled back + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blks_read</code> <code class="type">bigint</code> + </p> + <p> + Number of disk blocks read in this database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blks_hit</code> <code class="type">bigint</code> + </p> + <p> + Number of times disk blocks were found already in the buffer + cache, so that a read was not necessary (this only includes hits in the + PostgreSQL buffer cache, not the operating system's file system cache) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">tup_returned</code> <code class="type">bigint</code> + </p> + <p> + Number of live rows fetched by sequential scans and index entries returned by index scans in this database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">tup_fetched</code> <code class="type">bigint</code> + </p> + <p> + Number of live rows fetched by index scans in this database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">tup_inserted</code> <code class="type">bigint</code> + </p> + <p> + Number of rows inserted by queries in this database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">tup_updated</code> <code class="type">bigint</code> + </p> + <p> + Number of rows updated by queries in this database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">tup_deleted</code> <code class="type">bigint</code> + </p> + <p> + Number of rows deleted by queries in this database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">conflicts</code> <code class="type">bigint</code> + </p> + <p> + Number of queries canceled due to conflicts with recovery + in this database. (Conflicts occur only on standby servers; see + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW" title="28.2.16. pg_stat_database_conflicts"> + <code class="structname">pg_stat_database_conflicts</code></a> for details.) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">temp_files</code> <code class="type">bigint</code> + </p> + <p> + Number of temporary files created by queries in this database. + All temporary files are counted, regardless of why the temporary file + was created (e.g., sorting or hashing), and regardless of the + <a class="xref" href="runtime-config-logging.html#GUC-LOG-TEMP-FILES">log_temp_files</a> setting. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">temp_bytes</code> <code class="type">bigint</code> + </p> + <p> + Total amount of data written to temporary files by queries in + this database. All temporary files are counted, regardless of why + the temporary file was created, and + regardless of the <a class="xref" href="runtime-config-logging.html#GUC-LOG-TEMP-FILES">log_temp_files</a> setting. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">deadlocks</code> <code class="type">bigint</code> + </p> + <p> + Number of deadlocks detected in this database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">checksum_failures</code> <code class="type">bigint</code> + </p> + <p> + Number of data page checksum failures detected in this + database (or on a shared object), or NULL if data checksums are not + enabled. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">checksum_last_failure</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time at which the last data page checksum failure was detected in + this database (or on a shared object), or NULL if data checksums are not + enabled. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blk_read_time</code> <code class="type">double precision</code> + </p> + <p> + Time spent reading data file blocks by backends in this database, + in milliseconds (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled, + otherwise zero) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blk_write_time</code> <code class="type">double precision</code> + </p> + <p> + Time spent writing data file blocks by backends in this database, + in milliseconds (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled, + otherwise zero) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">session_time</code> <code class="type">double precision</code> + </p> + <p> + Time spent by database sessions in this database, in milliseconds + (note that statistics are only updated when the state of a session + changes, so if sessions have been idle for a long time, this idle time + won't be included) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">active_time</code> <code class="type">double precision</code> + </p> + <p> + Time spent executing SQL statements in this database, in milliseconds + (this corresponds to the states <code class="literal">active</code> and + <code class="literal">fastpath function call</code> in + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW" title="28.2.3. pg_stat_activity"> + <code class="structname">pg_stat_activity</code></a>) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idle_in_transaction_time</code> <code class="type">double precision</code> + </p> + <p> + Time spent idling while in a transaction in this database, in milliseconds + (this corresponds to the states <code class="literal">idle in transaction</code> and + <code class="literal">idle in transaction (aborted)</code> in + <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW" title="28.2.3. pg_stat_activity"> + <code class="structname">pg_stat_activity</code></a>) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sessions</code> <code class="type">bigint</code> + </p> + <p> + Total number of sessions established to this database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sessions_abandoned</code> <code class="type">bigint</code> + </p> + <p> + Number of database sessions to this database that were terminated + because connection to the client was lost + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sessions_fatal</code> <code class="type">bigint</code> + </p> + <p> + Number of database sessions to this database that were terminated + by fatal errors + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">sessions_killed</code> <code class="type">bigint</code> + </p> + <p> + Number of database sessions to this database that were terminated + by operator intervention + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time at which these statistics were last reset + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.16. <code class="structname">pg_stat_database_conflicts</code></h3></div></div></div><a id="id-1.6.15.7.20.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_database_conflicts</code> view will contain + one row per database, showing database-wide statistics about + query cancels occurring due to conflicts with recovery on standby servers. + This view will only contain information on standby servers, since + conflicts do not occur on primary servers. + </p><div class="table" id="PG-STAT-DATABASE-CONFLICTS-VIEW"><p class="title"><strong>Table 28.26. <code class="structname">pg_stat_database_conflicts</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_database_conflicts View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">datid</code> <code class="type">oid</code> + </p> + <p> + OID of a database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">datname</code> <code class="type">name</code> + </p> + <p> + Name of this database + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">confl_tablespace</code> <code class="type">bigint</code> + </p> + <p> + Number of queries in this database that have been canceled due to + dropped tablespaces + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">confl_lock</code> <code class="type">bigint</code> + </p> + <p> + Number of queries in this database that have been canceled due to + lock timeouts + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">confl_snapshot</code> <code class="type">bigint</code> + </p> + <p> + Number of queries in this database that have been canceled due to + old snapshots + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">confl_bufferpin</code> <code class="type">bigint</code> + </p> + <p> + Number of queries in this database that have been canceled due to + pinned buffers + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">confl_deadlock</code> <code class="type">bigint</code> + </p> + <p> + Number of queries in this database that have been canceled due to + deadlocks + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-ALL-TABLES-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.17. <code class="structname">pg_stat_all_tables</code></h3></div></div></div><a id="id-1.6.15.7.21.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_all_tables</code> view will contain + one row for each table in the current database (including TOAST + tables), showing statistics about accesses to that specific table. The + <code class="structname">pg_stat_user_tables</code> and + <code class="structname">pg_stat_sys_tables</code> views + contain the same information, + but filtered to only show user and system tables respectively. + </p><div class="table" id="PG-STAT-ALL-TABLES-VIEW"><p class="title"><strong>Table 28.27. <code class="structname">pg_stat_all_tables</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_all_tables View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relid</code> <code class="type">oid</code> + </p> + <p> + OID of a table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">schemaname</code> <code class="type">name</code> + </p> + <p> + Name of the schema that this table is in + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relname</code> <code class="type">name</code> + </p> + <p> + Name of this table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">seq_scan</code> <code class="type">bigint</code> + </p> + <p> + Number of sequential scans initiated on this table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">seq_tup_read</code> <code class="type">bigint</code> + </p> + <p> + Number of live rows fetched by sequential scans + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idx_scan</code> <code class="type">bigint</code> + </p> + <p> + Number of index scans initiated on this table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idx_tup_fetch</code> <code class="type">bigint</code> + </p> + <p> + Number of live rows fetched by index scans + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">n_tup_ins</code> <code class="type">bigint</code> + </p> + <p> + Number of rows inserted + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">n_tup_upd</code> <code class="type">bigint</code> + </p> + <p> + Number of rows updated (includes <a class="link" href="storage-hot.html" title="73.7. Heap-Only Tuples (HOT)">HOT updated rows</a>) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">n_tup_del</code> <code class="type">bigint</code> + </p> + <p> + Number of rows deleted + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">n_tup_hot_upd</code> <code class="type">bigint</code> + </p> + <p> + Number of rows HOT updated (i.e., with no separate index + update required) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">n_live_tup</code> <code class="type">bigint</code> + </p> + <p> + Estimated number of live rows + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">n_dead_tup</code> <code class="type">bigint</code> + </p> + <p> + Estimated number of dead rows + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">n_mod_since_analyze</code> <code class="type">bigint</code> + </p> + <p> + Estimated number of rows modified since this table was last analyzed + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">n_ins_since_vacuum</code> <code class="type">bigint</code> + </p> + <p> + Estimated number of rows inserted since this table was last vacuumed + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_vacuum</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Last time at which this table was manually vacuumed + (not counting <code class="command">VACUUM FULL</code>) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_autovacuum</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Last time at which this table was vacuumed by the autovacuum + daemon + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_analyze</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Last time at which this table was manually analyzed + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">last_autoanalyze</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Last time at which this table was analyzed by the autovacuum + daemon + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">vacuum_count</code> <code class="type">bigint</code> + </p> + <p> + Number of times this table has been manually vacuumed + (not counting <code class="command">VACUUM FULL</code>) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">autovacuum_count</code> <code class="type">bigint</code> + </p> + <p> + Number of times this table has been vacuumed by the autovacuum + daemon + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">analyze_count</code> <code class="type">bigint</code> + </p> + <p> + Number of times this table has been manually analyzed + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">autoanalyze_count</code> <code class="type">bigint</code> + </p> + <p> + Number of times this table has been analyzed by the autovacuum + daemon + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-ALL-INDEXES-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.18. <code class="structname">pg_stat_all_indexes</code></h3></div></div></div><a id="id-1.6.15.7.22.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_all_indexes</code> view will contain + one row for each index in the current database, + showing statistics about accesses to that specific index. The + <code class="structname">pg_stat_user_indexes</code> and + <code class="structname">pg_stat_sys_indexes</code> views + contain the same information, + but filtered to only show user and system indexes respectively. + </p><div class="table" id="PG-STAT-ALL-INDEXES-VIEW"><p class="title"><strong>Table 28.28. <code class="structname">pg_stat_all_indexes</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_all_indexes View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relid</code> <code class="type">oid</code> + </p> + <p> + OID of the table for this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">indexrelid</code> <code class="type">oid</code> + </p> + <p> + OID of this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">schemaname</code> <code class="type">name</code> + </p> + <p> + Name of the schema this index is in + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relname</code> <code class="type">name</code> + </p> + <p> + Name of the table for this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">indexrelname</code> <code class="type">name</code> + </p> + <p> + Name of this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idx_scan</code> <code class="type">bigint</code> + </p> + <p> + Number of index scans initiated on this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idx_tup_read</code> <code class="type">bigint</code> + </p> + <p> + Number of index entries returned by scans on this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idx_tup_fetch</code> <code class="type">bigint</code> + </p> + <p> + Number of live table rows fetched by simple index scans using this + index + </p></td></tr></tbody></table></div></div><br class="table-break" /><p> + Indexes can be used by simple index scans, <span class="quote">“<span class="quote">bitmap</span>”</span> index scans, + and the optimizer. In a bitmap scan + the output of several indexes can be combined via AND or OR rules, + so it is difficult to associate individual heap row fetches + with specific indexes when a bitmap scan is used. Therefore, a bitmap + scan increments the + <code class="structname">pg_stat_all_indexes</code>.<code class="structfield">idx_tup_read</code> + count(s) for the index(es) it uses, and it increments the + <code class="structname">pg_stat_all_tables</code>.<code class="structfield">idx_tup_fetch</code> + count for the table, but it does not affect + <code class="structname">pg_stat_all_indexes</code>.<code class="structfield">idx_tup_fetch</code>. + The optimizer also accesses indexes to check for supplied constants + whose values are outside the recorded range of the optimizer statistics + because the optimizer statistics might be stale. + </p><div class="note"><h3 class="title">Note</h3><p> + The <code class="structfield">idx_tup_read</code> and <code class="structfield">idx_tup_fetch</code> counts + can be different even without any use of bitmap scans, + because <code class="structfield">idx_tup_read</code> counts + index entries retrieved from the index while <code class="structfield">idx_tup_fetch</code> + counts live rows fetched from the table. The latter will be less if any + dead or not-yet-committed rows are fetched using the index, or if any + heap fetches are avoided by means of an index-only scan. + </p></div></div><div class="sect2" id="MONITORING-PG-STATIO-ALL-TABLES-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.19. <code class="structname">pg_statio_all_tables</code></h3></div></div></div><a id="id-1.6.15.7.23.2" class="indexterm"></a><p> + The <code class="structname">pg_statio_all_tables</code> view will contain + one row for each table in the current database (including TOAST + tables), showing statistics about I/O on that specific table. The + <code class="structname">pg_statio_user_tables</code> and + <code class="structname">pg_statio_sys_tables</code> views + contain the same information, + but filtered to only show user and system tables respectively. + </p><div class="table" id="PG-STATIO-ALL-TABLES-VIEW"><p class="title"><strong>Table 28.29. <code class="structname">pg_statio_all_tables</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_statio_all_tables View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relid</code> <code class="type">oid</code> + </p> + <p> + OID of a table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">schemaname</code> <code class="type">name</code> + </p> + <p> + Name of the schema that this table is in + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relname</code> <code class="type">name</code> + </p> + <p> + Name of this table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">heap_blks_read</code> <code class="type">bigint</code> + </p> + <p> + Number of disk blocks read from this table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">heap_blks_hit</code> <code class="type">bigint</code> + </p> + <p> + Number of buffer hits in this table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idx_blks_read</code> <code class="type">bigint</code> + </p> + <p> + Number of disk blocks read from all indexes on this table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idx_blks_hit</code> <code class="type">bigint</code> + </p> + <p> + Number of buffer hits in all indexes on this table + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">toast_blks_read</code> <code class="type">bigint</code> + </p> + <p> + Number of disk blocks read from this table's TOAST table (if any) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">toast_blks_hit</code> <code class="type">bigint</code> + </p> + <p> + Number of buffer hits in this table's TOAST table (if any) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">tidx_blks_read</code> <code class="type">bigint</code> + </p> + <p> + Number of disk blocks read from this table's TOAST table indexes (if any) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">tidx_blks_hit</code> <code class="type">bigint</code> + </p> + <p> + Number of buffer hits in this table's TOAST table indexes (if any) + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STATIO-ALL-INDEXES-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.20. <code class="structname">pg_statio_all_indexes</code></h3></div></div></div><a id="id-1.6.15.7.24.2" class="indexterm"></a><p> + The <code class="structname">pg_statio_all_indexes</code> view will contain + one row for each index in the current database, + showing statistics about I/O on that specific index. The + <code class="structname">pg_statio_user_indexes</code> and + <code class="structname">pg_statio_sys_indexes</code> views + contain the same information, + but filtered to only show user and system indexes respectively. + </p><div class="table" id="PG-STATIO-ALL-INDEXES-VIEW"><p class="title"><strong>Table 28.30. <code class="structname">pg_statio_all_indexes</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_statio_all_indexes View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relid</code> <code class="type">oid</code> + </p> + <p> + OID of the table for this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">indexrelid</code> <code class="type">oid</code> + </p> + <p> + OID of this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">schemaname</code> <code class="type">name</code> + </p> + <p> + Name of the schema this index is in + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relname</code> <code class="type">name</code> + </p> + <p> + Name of the table for this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">indexrelname</code> <code class="type">name</code> + </p> + <p> + Name of this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idx_blks_read</code> <code class="type">bigint</code> + </p> + <p> + Number of disk blocks read from this index + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">idx_blks_hit</code> <code class="type">bigint</code> + </p> + <p> + Number of buffer hits in this index + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STATIO-ALL-SEQUENCES-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.21. <code class="structname">pg_statio_all_sequences</code></h3></div></div></div><a id="id-1.6.15.7.25.2" class="indexterm"></a><p> + The <code class="structname">pg_statio_all_sequences</code> view will contain + one row for each sequence in the current database, + showing statistics about I/O on that specific sequence. + </p><div class="table" id="PG-STATIO-ALL-SEQUENCES-VIEW"><p class="title"><strong>Table 28.31. <code class="structname">pg_statio_all_sequences</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_statio_all_sequences View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relid</code> <code class="type">oid</code> + </p> + <p> + OID of a sequence + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">schemaname</code> <code class="type">name</code> + </p> + <p> + Name of the schema this sequence is in + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">relname</code> <code class="type">name</code> + </p> + <p> + Name of this sequence + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blks_read</code> <code class="type">bigint</code> + </p> + <p> + Number of disk blocks read from this sequence + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blks_hit</code> <code class="type">bigint</code> + </p> + <p> + Number of buffer hits in this sequence + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-USER-FUNCTIONS-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.22. <code class="structname">pg_stat_user_functions</code></h3></div></div></div><a id="id-1.6.15.7.26.2" class="indexterm"></a><p> + The <code class="structname">pg_stat_user_functions</code> view will contain + one row for each tracked function, showing statistics about executions of + that function. The <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-FUNCTIONS">track_functions</a> parameter + controls exactly which functions are tracked. + </p><div class="table" id="PG-STAT-USER-FUNCTIONS-VIEW"><p class="title"><strong>Table 28.32. <code class="structname">pg_stat_user_functions</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_user_functions View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">funcid</code> <code class="type">oid</code> + </p> + <p> + OID of a function + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">schemaname</code> <code class="type">name</code> + </p> + <p> + Name of the schema this function is in + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">funcname</code> <code class="type">name</code> + </p> + <p> + Name of this function + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">calls</code> <code class="type">bigint</code> + </p> + <p> + Number of times this function has been called + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">total_time</code> <code class="type">double precision</code> + </p> + <p> + Total time spent in this function and all other functions + called by it, in milliseconds + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">self_time</code> <code class="type">double precision</code> + </p> + <p> + Total time spent in this function itself, not including + other functions called by it, in milliseconds + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-SLRU-VIEW"><div class="titlepage"><div><div><h3 class="title">28.2.23. <code class="structname">pg_stat_slru</code></h3></div></div></div><a id="id-1.6.15.7.27.2" class="indexterm"></a><a id="id-1.6.15.7.27.3" class="indexterm"></a><p> + <span class="productname">PostgreSQL</span> accesses certain on-disk information + via <em class="firstterm">SLRU</em> (simple least-recently-used) caches. + The <code class="structname">pg_stat_slru</code> view will contain + one row for each tracked SLRU cache, showing statistics about access + to cached pages. + </p><div class="table" id="PG-STAT-SLRU-VIEW"><p class="title"><strong>Table 28.33. <code class="structname">pg_stat_slru</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_slru View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">name</code> <code class="type">text</code> + </p> + <p> + Name of the SLRU + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blks_zeroed</code> <code class="type">bigint</code> + </p> + <p> + Number of blocks zeroed during initializations + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blks_hit</code> <code class="type">bigint</code> + </p> + <p> + Number of times disk blocks were found already in the SLRU, + so that a read was not necessary (this only includes hits in the + SLRU, not the operating system's file system cache) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blks_read</code> <code class="type">bigint</code> + </p> + <p> + Number of disk blocks read for this SLRU + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blks_written</code> <code class="type">bigint</code> + </p> + <p> + Number of disk blocks written for this SLRU + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">blks_exists</code> <code class="type">bigint</code> + </p> + <p> + Number of blocks checked for existence for this SLRU + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">flushes</code> <code class="type">bigint</code> + </p> + <p> + Number of flushes of dirty data for this SLRU + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">truncates</code> <code class="type">bigint</code> + </p> + <p> + Number of truncates for this SLRU + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code> + </p> + <p> + Time at which these statistics were last reset + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-STATS-FUNCTIONS"><div class="titlepage"><div><div><h3 class="title">28.2.24. Statistics Functions</h3></div></div></div><p> + Other ways of looking at the statistics can be set up by writing + queries that use the same underlying statistics access functions used by + the standard views shown above. For details such as the functions' names, + consult the definitions of the standard views. (For example, in + <span class="application">psql</span> you could issue <code class="literal">\d+ pg_stat_activity</code>.) + The access functions for per-database statistics take a database OID as an + argument to identify which database to report on. + The per-table and per-index functions take a table or index OID. + The functions for per-function statistics take a function OID. + Note that only tables, indexes, and functions in the current database + can be seen with these functions. + </p><p> + Additional functions related to the cumulative statistics system are listed + in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-FUNCS-TABLE" title="Table 28.34. Additional Statistics Functions">Table 28.34</a>. + </p><div class="table" id="MONITORING-STATS-FUNCS-TABLE"><p class="title"><strong>Table 28.34. Additional Statistics Functions</strong></p><div class="table-contents"><table class="table" summary="Additional Statistics Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature"> + Function + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature"> + <code class="function">pg_backend_pid</code> () + → <code class="returnvalue">integer</code> + </p> + <p> + Returns the process ID of the server process attached to the current + session. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.2.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_activity</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">setof record</code> + </p> + <p> + Returns a record of information about the backend with the specified + process ID, or one record for each active backend in the system + if <code class="literal">NULL</code> is specified. The fields returned are a + subset of those in the <code class="structname">pg_stat_activity</code> view. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.3.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_snapshot_timestamp</code> () + → <code class="returnvalue">timestamp with time zone</code> + </p> + <p> + Returns the timestamp of the current statistics snapshot, or NULL if + no statistics snapshot has been taken. A snapshot is taken the first + time cumulative statistics are accessed in a transaction if + <code class="varname">stats_fetch_consistency</code> is set to + <code class="literal">snapshot</code> + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.4.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_xact_blocks_fetched</code> ( <code class="type">oid</code> ) + → <code class="returnvalue">bigint</code> + </p> + <p> + Returns the number of block read requests for table or index, in the + current transaction. This number minus + <code class="function">pg_stat_get_xact_blocks_hit</code> gives the number of + kernel <code class="function">read()</code> calls; the number of actual + physical reads is usually lower due to kernel-level buffering. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.5.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_xact_blocks_hit</code> ( <code class="type">oid</code> ) + → <code class="returnvalue">bigint</code> + </p> + <p> + Returns the number of block read requests for table or index, in the + current transaction, found in cache (not triggering kernel + <code class="function">read()</code> calls). + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.6.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_clear_snapshot</code> () + → <code class="returnvalue">void</code> + </p> + <p> + Discards the current statistics snapshot or cached information. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.7.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_reset</code> () + → <code class="returnvalue">void</code> + </p> + <p> + Resets all statistics counters for the current database to zero. + </p> + <p> + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.8.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_reset_shared</code> ( <code class="type">text</code> ) + → <code class="returnvalue">void</code> + </p> + <p> + Resets some cluster-wide statistics counters to zero, depending on the + argument. The argument can be <code class="literal">bgwriter</code> to reset + all the counters shown in + the <code class="structname">pg_stat_bgwriter</code> + view, <code class="literal">archiver</code> to reset all the counters shown in + the <code class="structname">pg_stat_archiver</code> view, + <code class="literal">wal</code> to reset all the counters shown in the + <code class="structname">pg_stat_wal</code> view or + <code class="literal">recovery_prefetch</code> to reset all the counters shown + in the <code class="structname">pg_stat_recovery_prefetch</code> view. + </p> + <p> + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.9.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_reset_single_table_counters</code> ( <code class="type">oid</code> ) + → <code class="returnvalue">void</code> + </p> + <p> + Resets statistics for a single table or index in the current database + or shared across all databases in the cluster to zero. + </p> + <p> + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.10.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_reset_single_function_counters</code> ( <code class="type">oid</code> ) + → <code class="returnvalue">void</code> + </p> + <p> + Resets statistics for a single function in the current database to + zero. + </p> + <p> + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.11.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_reset_slru</code> ( <code class="type">text</code> ) + → <code class="returnvalue">void</code> + </p> + <p> + Resets statistics to zero for a single SLRU cache, or for all SLRUs in + the cluster. If the argument is NULL, all counters shown in + the <code class="structname">pg_stat_slru</code> view for all SLRU caches are + reset. The argument can be one of + <code class="literal">CommitTs</code>, + <code class="literal">MultiXactMember</code>, + <code class="literal">MultiXactOffset</code>, + <code class="literal">Notify</code>, + <code class="literal">Serial</code>, + <code class="literal">Subtrans</code>, or + <code class="literal">Xact</code> + to reset the counters for only that entry. + If the argument is <code class="literal">other</code> (or indeed, any + unrecognized name), then the counters for all other SLRU caches, such + as extension-defined caches, are reset. + </p> + <p> + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.12.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_reset_replication_slot</code> ( <code class="type">text</code> ) + → <code class="returnvalue">void</code> + </p> + <p> + Resets statistics of the replication slot defined by the argument. If + the argument is <code class="literal">NULL</code>, resets statistics for all + the replication slots. + </p> + <p> + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.4.2.2.13.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_reset_subscription_stats</code> ( <code class="type">oid</code> ) + → <code class="returnvalue">void</code> + </p> + <p> + Resets statistics for a single subscription shown in the + <code class="structname">pg_stat_subscription_stats</code> view to zero. If + the argument is <code class="literal">NULL</code>, reset statistics for all + subscriptions. + </p> + <p> + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + </p></td></tr></tbody></table></div></div><br class="table-break" /><div class="warning"><h3 class="title">Warning</h3><p> + Using <code class="function">pg_stat_reset()</code> also resets counters that + autovacuum uses to determine when to trigger a vacuum or an analyze. + Resetting these counters can cause autovacuum to not perform necessary + work, which can cause problems such as table bloat or out-dated + table statistics. A database-wide <code class="command">ANALYZE</code> is + recommended after the statistics have been reset. + </p></div><p> + <code class="function">pg_stat_get_activity</code>, the underlying function of + the <code class="structname">pg_stat_activity</code> view, returns a set of records + containing all the available information about each backend process. + Sometimes it may be more convenient to obtain just a subset of this + information. In such cases, an older set of per-backend statistics + access functions can be used; these are shown in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-BACKEND-FUNCS-TABLE" title="Table 28.35. Per-Backend Statistics Functions">Table 28.35</a>. + These access functions use a backend ID number, which ranges from one + to the number of currently active backends. + The function <code class="function">pg_stat_get_backend_idset</code> provides a + convenient way to generate one row for each active backend for + invoking these functions. For example, to show the <acronym class="acronym">PID</acronym>s and + current queries of all backends: + +</p><pre class="programlisting"> +SELECT pg_stat_get_backend_pid(s.backendid) AS pid, + pg_stat_get_backend_activity(s.backendid) AS query + FROM (SELECT pg_stat_get_backend_idset() AS backendid) AS s; +</pre><p> + </p><div class="table" id="MONITORING-STATS-BACKEND-FUNCS-TABLE"><p class="title"><strong>Table 28.35. Per-Backend Statistics Functions</strong></p><div class="table-contents"><table class="table" summary="Per-Backend Statistics Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature"> + Function + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.1.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_idset</code> () + → <code class="returnvalue">setof integer</code> + </p> + <p> + Returns the set of currently active backend ID numbers (from 1 to the + number of active backends). + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.2.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_activity</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">text</code> + </p> + <p> + Returns the text of this backend's most recent query. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.3.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_activity_start</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">timestamp with time zone</code> + </p> + <p> + Returns the time when the backend's most recent query was started. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.4.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_client_addr</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">inet</code> + </p> + <p> + Returns the IP address of the client connected to this backend. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.5.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_client_port</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">integer</code> + </p> + <p> + Returns the TCP port number that the client is using for communication. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.6.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_dbid</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">oid</code> + </p> + <p> + Returns the OID of the database this backend is connected to. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.7.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_pid</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">integer</code> + </p> + <p> + Returns the process ID of this backend. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.8.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_start</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">timestamp with time zone</code> + </p> + <p> + Returns the time when this process was started. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.9.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_userid</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">oid</code> + </p> + <p> + Returns the OID of the user logged into this backend. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.10.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_wait_event_type</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">text</code> + </p> + <p> + Returns the wait event type name if this backend is currently waiting, + otherwise NULL. See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TABLE" title="Table 28.4. Wait Event Types">Table 28.4</a> for details. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.11.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_wait_event</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">text</code> + </p> + <p> + Returns the wait event name if this backend is currently waiting, + otherwise NULL. 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> through + <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TIMEOUT-TABLE" title="Table 28.13. Wait Events of Type Timeout">Table 28.13</a>. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <a id="id-1.6.15.7.28.7.2.2.12.1.1.1" class="indexterm"></a> + <code class="function">pg_stat_get_backend_xact_start</code> ( <code class="type">integer</code> ) + → <code class="returnvalue">timestamp with time zone</code> + </p> + <p> + Returns the time when the backend's current transaction was started. + </p></td></tr></tbody></table></div></div><br class="table-break" /></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="monitoring-ps.html" title="28.1. Standard Unix Tools">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="monitoring.html" title="Chapter 28. Monitoring Database Activity">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="monitoring-locks.html" title="28.3. 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