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Postgres FD Implementation
Commit 4fa8bd39 authored by Tom Lane's avatar Tom Lane
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Doc: split up wait_event table. 

The previous design for this table didn't really work in narrow views,
such as PDF output; besides which its reliance on large morerows
values made it a pain to maintain (cf ab3e4fbd, for example).

I experimented with a couple of ways to fix it, but the best and
simplest is to split it up into a separate table for each event
type category.

I also rearranged the event ordering to be strictly alphabetical,
as nobody would ever be able to find entries otherwise.

There is work afoot to revise the set of event names described
in this table, but this commit just changes the layout, not the
contents.

In passing, add a missing entry to pg_locks.locktype,
and cross-reference that to the related wait event list.

Discussion: https://postgr.es/m/6916.1589146280@sss.pgh.pa.us
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doc/src/sgml/catalogs.sgml
View file @ 4fa8bd39
......@@ -10238,9 +10238,11 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
<literal>tuple</literal>,
<literal>transactionid</literal>,
<literal>virtualxid</literal>,
<literal>speculative token</literal>,
<literal>object</literal>,
<literal>userlock</literal>, or
<literal>advisory</literal>
<literal>advisory</literal>.
(See also <xref linkend="wait-event-lock-table"/>.)
</para></entry>
</row>
......
doc/src/sgml/monitoring.sgml
View file @ 4fa8bd39
......@@ -775,1130 +775,1314 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
</para>
<para>
The type of event for which the backend is waiting, if any;
otherwise NULL. Possible values are:
otherwise NULL. See <xref linkend="wait-event-table"/>.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>wait_event</structfield> <type>text</type>
</para>
<para>
Wait event name if backend is currently waiting, otherwise NULL.
See <xref linkend="wait-event-activity-table"/> through
<xref linkend="wait-event-timeout-table"/>.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>state</structfield> <type>text</type>
</para>
<para>
Current overall state of this backend.
Possible values are:
<itemizedlist>
<listitem>
<para>
<literal>LWLock</literal>: The backend is waiting for a lightweight lock.
Each such lock protects a particular data structure in shared memory.
<literal>wait_event</literal> 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.)
</para>
</listitem>
<listitem>
<para>
<literal>Lock</literal>: The backend 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. <literal>wait_event</literal> will
identify the type of lock awaited.
</para>
</listitem>
<listitem>
<para>
<literal>BufferPin</literal>: The server process is waiting to access to
a data buffer during a period when no other process can be
examining that buffer. Buffer pin waits can be protracted if
another process holds an open cursor which last read data from the
buffer in question.
</para>
</listitem>
<listitem>
<para>
<literal>Activity</literal>: The server process is idle. This is used by
system processes waiting for activity in their main processing loop.
<literal>wait_event</literal> will identify the specific wait point.
<para>
<literal>active</literal>: The backend is executing a query.
</para>
</listitem>
<listitem>
<para>
<literal>Extension</literal>: The server process is waiting for activity
in an extension module. This category is useful for modules to
track custom waiting points.
<literal>idle</literal>: The backend is waiting for a new client command.
</para>
</listitem>
<listitem>
<para>
<literal>Client</literal>: The server process is waiting for some activity
on a socket from user applications, and that the server expects
something to happen that is independent from its internal processes.
<literal>wait_event</literal> will identify the specific wait point.
<literal>idle in transaction</literal>: The backend is in a transaction,
but is not currently executing a query.
</para>
</listitem>
<listitem>
<para>
<literal>IPC</literal>: The server process is waiting for some activity
from another process in the server. <literal>wait_event</literal> will
identify the specific wait point.
<literal>idle in transaction (aborted)</literal>: This state is similar to
<literal>idle in transaction</literal>, except one of the statements in
the transaction caused an error.
</para>
</listitem>
<listitem>
<para>
<literal>Timeout</literal>: The server process is waiting for a timeout
to expire. <literal>wait_event</literal> will identify the specific wait
point.
<literal>fastpath function call</literal>: The backend is executing a
fast-path function.
</para>
</listitem>
<listitem>
<para>
<literal>IO</literal>: The server process is waiting for a IO to complete.
<literal>wait_event</literal> will identify the specific wait point.
<literal>disabled</literal>: This state is reported if <xref linkend="guc-track-activities"/> is disabled in this backend.
</para>
</listitem>
</listitem>
</itemizedlist>
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>wait_event</structfield> <type>text</type>
</para>
<para>
Wait event name if backend is currently waiting, otherwise NULL.
See <xref linkend="wait-event-table"/> for details.
</para></entry>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>backend_xid</structfield> <type>xid</type>
</para>
<para>
Top-level transaction identifier of this backend, if any.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>backend_xmin</structfield> <type>xid</type>
</para>
<para>
The current backend's <literal>xmin</literal> horizon.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>query</structfield> <type>text</type>
</para>
<para>
Text of this backend's most recent query. If
<structfield>state</structfield> is <literal>active</literal> 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
characters; this value can be changed via the parameter
<xref linkend="guc-track-activity-query-size"/>.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>backend_type</structfield> <type>text</type>
</para>
<para>
Type of current backend. Possible types are
<literal>autovacuum launcher</literal>, <literal>autovacuum worker</literal>,
<literal>logical replication launcher</literal>,
<literal>logical replication worker</literal>,
<literal>parallel worker</literal>, <literal>background writer</literal>,
<literal>client backend</literal>, <literal>checkpointer</literal>,
<literal>startup</literal>, <literal>walreceiver</literal>,
<literal>walsender</literal> and <literal>walwriter</literal>.
In addition, background workers registered by extensions may have
additional types.
</para></entry>
</row>
</tbody>
</tgroup>
</table>
<para>
The <structname>pg_stat_activity</structname> view will have one row
per server process, showing information related to
the current activity of that process.
</para>
<note>
<para>
The <structfield>wait_event</structfield> and <structfield>state</structfield> columns are
independent. If a backend is in the <literal>active</literal> state,
it may or may not be <literal>waiting</literal> on some event. If the state
is <literal>active</literal> and <structfield>wait_event</structfield> is non-null, it
means that a query is being executed, but is being blocked somewhere
in the system.
</para>
</note>
<table id="wait-event-table">
<title>Wait Event Types</title>
<tgroup cols="2">
<thead>
<row>
<entry>Wait Event Type</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>Activity</literal></entry>
<entry>The server process is idle. This is used by
system processes waiting for activity in their main processing loop.
<literal>wait_event</literal> will identify the specific wait point.
See <xref linkend="wait-event-activity-table"/>.
</entry>
</row>
<row>
<entry><literal>BufferPin</literal></entry>
<entry>The server process is waiting to access to
a data buffer during a period when no other process can be
examining that buffer. Buffer pin waits can be protracted if
another process holds an open cursor which last read data from the
buffer in question. See <xref linkend="wait-event-bufferpin-table"/>.
</entry>
</row>
<row>
<entry><literal>Client</literal></entry>
<entry>The server process is waiting for some activity
on a socket from user applications, and that the server expects
something to happen that is independent from its internal processes.
<literal>wait_event</literal> will identify the specific wait point.
See <xref linkend="wait-event-client-table"/>.
</entry>
</row>
<row>
<entry><literal>Extension</literal></entry>
<entry>The server process is waiting for activity
in an extension module. This category is useful for modules to
track custom waiting points.
See <xref linkend="wait-event-extension-table"/>.
</entry>
</row>
<row>
<entry><literal>IO</literal></entry>
<entry>The server process is waiting for a IO to complete.
<literal>wait_event</literal> will identify the specific wait point.
See <xref linkend="wait-event-io-table"/>.
</entry>
</row>
<row>
<entry><literal>IPC</literal></entry>
<entry>The server process is waiting for some activity
from another process in the server. <literal>wait_event</literal> will
identify the specific wait point.
See <xref linkend="wait-event-ipc-table"/>.
</entry>
</row>
<row>
<entry><literal>Lock</literal></entry>
<entry>The backend 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. <literal>wait_event</literal>
will identify the type of lock awaited.
See <xref linkend="wait-event-lock-table"/>.
</entry>
</row>
<row>
<entry><literal>LWLock</literal></entry>
<entry> The backend is waiting for a lightweight lock.
Each such lock protects a particular data structure in shared memory.
<literal>wait_event</literal> 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 <xref linkend="wait-event-lwlock-table"/>.
</entry>
</row>
<row>
<entry><literal>Timeout</literal></entry>
<entry>The server process is waiting for a timeout
to expire. <literal>wait_event</literal> will identify the specific wait
point. See <xref linkend="wait-event-timeout-table"/>.
</entry>
</row>
</tbody>
</tgroup>
</table>
<table id="wait-event-activity-table">
<title>Wait Events of Type <literal>Activity</literal></title>
<tgroup cols="2">
<thead>
<row>
<entry><literal>Activity</literal> Wait Event</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>ArchiverMain</literal></entry>
<entry>Waiting in main loop of the archiver process.</entry>
</row>
<row>
<entry><literal>AutoVacuumMain</literal></entry>
<entry>Waiting in main loop of autovacuum launcher process.</entry>
</row>
<row>
<entry><literal>BgWriterHibernate</literal></entry>
<entry>Waiting in background writer process, hibernating.</entry>
</row>
<row>
<entry><literal>BgWriterMain</literal></entry>
<entry>Waiting in main loop of background writer process background
worker.</entry>
</row>
<row>
<entry><literal>CheckpointerMain</literal></entry>
<entry>Waiting in main loop of checkpointer process.</entry>
</row>
<row>
<entry><literal>LogicalApplyMain</literal></entry>
<entry>Waiting in main loop of logical apply process.</entry>
</row>
<row>
<entry><literal>LogicalLauncherMain</literal></entry>
<entry>Waiting in main loop of logical launcher process.</entry>
</row>
<row>
<entry><literal>PgStatMain</literal></entry>
<entry>Waiting in main loop of the statistics collector process.</entry>
</row>
<row>
<entry><literal>RecoveryWalStream</literal></entry>
<entry>Waiting for WAL from a stream at recovery.</entry>
</row>
<row>
<entry><literal>SysLoggerMain</literal></entry>
<entry>Waiting in main loop of syslogger process.</entry>
</row>
<row>
<entry><literal>WalReceiverMain</literal></entry>
<entry>Waiting in main loop of WAL receiver process.</entry>
</row>
<row>
<entry><literal>WalSenderMain</literal></entry>
<entry>Waiting in main loop of WAL sender process.</entry>
</row>
<row>
<entry><literal>WalWriterMain</literal></entry>
<entry>Waiting in main loop of WAL writer process.</entry>
</row>
</tbody>
</tgroup>
</table>
<table id="wait-event-bufferpin-table">
<title>Wait Events of Type <literal>BufferPin</literal></title>
<tgroup cols="2">
<thead>
<row>
<entry><literal>BufferPin</literal> Wait Event</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>BufferPin</literal></entry>
<entry>Waiting to acquire a pin on a buffer.</entry>
</row>
</tbody>
</tgroup>
</table>
<table id="wait-event-client-table">
<title>Wait Events of Type <literal>Client</literal></title>
<tgroup cols="2">
<thead>
<row>
<entry><literal>Client</literal> Wait Event</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>ClientRead</literal></entry>
<entry>Waiting to read data from the client.</entry>
</row>
<row>
<entry><literal>ClientWrite</literal></entry>
<entry>Waiting to write data to the client.</entry>
</row>
<row>
<entry><literal>GSSOpenServer</literal></entry>
<entry>Waiting to read data from the client while establishing the GSSAPI
session.</entry>
</row>
<row>
<entry><literal>LibPQWalReceiverConnect</literal></entry>
<entry>Waiting in WAL receiver to establish connection to remote
server.</entry>
</row>
<row>
<entry><literal>LibPQWalReceiverReceive</literal></entry>
<entry>Waiting in WAL receiver to receive data from remote server.</entry>
</row>
<row>
<entry><literal>SSLOpenServer</literal></entry>
<entry>Waiting for SSL while attempting connection.</entry>
</row>
<row>
<entry><literal>WalReceiverWaitStart</literal></entry>
<entry>Waiting for startup process to send initial data for streaming
replication.</entry>
</row>
<row>
<entry><literal>WalSenderWaitForWAL</literal></entry>
<entry>Waiting for WAL to be flushed in WAL sender process.</entry>
</row>
<row>
<entry><literal>WalSenderWriteData</literal></entry>
<entry>Waiting for any activity when processing replies from WAL
receiver in WAL sender process.</entry>
</row>
</tbody>
</tgroup>
</table>
<table id="wait-event-extension-table">
<title>Wait Events of Type <literal>Extension</literal></title>
<tgroup cols="2">
<thead>
<row>
<entry><literal>Extension</literal> Wait Event</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>Extension</literal></entry>
<entry>Waiting in an extension.</entry>
</row>
</tbody>
</tgroup>
</table>
<table id="wait-event-io-table">
<title>Wait Events of Type <literal>IO</literal></title>
<tgroup cols="2">
<thead>
<row>
<entry><literal>IO</literal> Wait Event</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>BufFileRead</literal></entry>
<entry>Waiting for a read from a buffered file.</entry>
</row>
<row>
<entry><literal>BufFileWrite</literal></entry>
<entry>Waiting for a write to a buffered file.</entry>
</row>
<row>
<entry><literal>ControlFileRead</literal></entry>
<entry>Waiting for a read from the control file.</entry>
</row>
<row>
<entry><literal>ControlFileSync</literal></entry>
<entry>Waiting for the control file to reach stable storage.</entry>
</row>
<row>
<entry><literal>ControlFileSyncUpdate</literal></entry>
<entry>Waiting for an update to the control file to reach stable
storage.</entry>
</row>
<row>
<entry><literal>ControlFileWrite</literal></entry>
<entry>Waiting for a write to the control file.</entry>
</row>
<row>
<entry><literal>ControlFileWriteUpdate</literal></entry>
<entry>Waiting for a write to update the control file.</entry>
</row>
<row>
<entry><literal>CopyFileRead</literal></entry>
<entry>Waiting for a read during a file copy operation.</entry>
</row>
<row>
<entry><literal>CopyFileWrite</literal></entry>
<entry>Waiting for a write during a file copy operation.</entry>
</row>
<row>
<entry><literal>DSMFillZeroWrite</literal></entry>
<entry>Waiting to write zero bytes to a dynamic shared memory backing
file.</entry>
</row>
<row>
<entry><literal>DataFileExtend</literal></entry>
<entry>Waiting for a relation data file to be extended.</entry>
</row>
<row>
<entry><literal>DataFileFlush</literal></entry>
<entry>Waiting for a relation data file to reach stable storage.</entry>
</row>
<row>
<entry><literal>DataFileImmediateSync</literal></entry>
<entry>Waiting for an immediate synchronization of a relation data file to
stable storage.</entry>
</row>
<row>
<entry><literal>DataFilePrefetch</literal></entry>
<entry>Waiting for an asynchronous prefetch from a relation data
file.</entry>
</row>
<row>
<entry><literal>DataFileRead</literal></entry>
<entry>Waiting for a read from a relation data file.</entry>
</row>
<row>
<entry><literal>DataFileSync</literal></entry>
<entry>Waiting for changes to a relation data file to reach stable storage.</entry>
</row>
<row>
<entry><literal>DataFileTruncate</literal></entry>
<entry>Waiting for a relation data file to be truncated.</entry>
</row>
<row>
<entry><literal>DataFileWrite</literal></entry>
<entry>Waiting for a write to a relation data file.</entry>
</row>
<row>
<entry><literal>LockFileAddToDataDirRead</literal></entry>
<entry>Waiting for a read while adding a line to the data directory lock
file.</entry>
</row>
<row>
<entry><literal>LockFileAddToDataDirSync</literal></entry>
<entry>Waiting for data to reach stable storage while adding a line to the
data directory lock file.</entry>
</row>
<row>
<entry><literal>LockFileAddToDataDirWrite</literal></entry>
<entry>Waiting for a write while adding a line to the data directory
lock file.</entry>
</row>
<row>
<entry><literal>LockFileCreateRead</literal></entry>
<entry>Waiting to read while creating the data directory lock
file.</entry>
</row>
<row>
<entry><literal>LockFileCreateSync</literal></entry>
<entry>Waiting for data to reach stable storage while creating the data
directory lock file.</entry>
</row>
<row>
<entry><literal>LockFileCreateWrite</literal></entry>
<entry>Waiting for a write while creating the data directory lock
file.</entry>
</row>
<row>
<entry><literal>LockFileReCheckDataDirRead</literal></entry>
<entry>Waiting for a read during recheck of the data directory lock
file.</entry>
</row>
<row>
<entry><literal>LogicalRewriteCheckpointSync</literal></entry>
<entry>Waiting for logical rewrite mappings to reach stable storage
during a checkpoint.</entry>
</row>
<row>
<entry><literal>LogicalRewriteMappingSync</literal></entry>
<entry>Waiting for mapping data to reach stable storage during a logical
rewrite.</entry>
</row>
<row>
<entry><literal>LogicalRewriteMappingWrite</literal></entry>
<entry>Waiting for a write of mapping data during a logical
rewrite.</entry>
</row>
<row>
<entry><literal>LogicalRewriteSync</literal></entry>
<entry>Waiting for logical rewrite mappings to reach stable
storage.</entry>
</row>
<row>
<entry><literal>LogicalRewriteTruncate</literal></entry>
<entry>Waiting for truncate of mapping data during a logical
rewrite.</entry>
</row>
<row>
<entry><literal>LogicalRewriteWrite</literal></entry>
<entry>Waiting for a write of logical rewrite mappings.</entry>
</row>
<row>
<entry><literal>ProcSignalBarrier</literal></entry>
<entry>Waiting for a barrier event to be processed by all
backends.</entry>
</row>
<row>
<entry><literal>RelationMapRead</literal></entry>
<entry>Waiting for a read of the relation map file.</entry>
</row>
<row>
<entry><literal>RelationMapSync</literal></entry>
<entry>Waiting for the relation map file to reach stable storage.</entry>
</row>
<row>
<entry><literal>RelationMapWrite</literal></entry>
<entry>Waiting for a write to the relation map file.</entry>
</row>
<row>
<entry><literal>ReorderBufferRead</literal></entry>
<entry>Waiting for a read during reorder buffer management.</entry>
</row>
<row>
<entry><literal>ReorderBufferWrite</literal></entry>
<entry>Waiting for a write during reorder buffer management.</entry>
</row>
<row>
<entry><literal>ReorderLogicalMappingRead</literal></entry>
<entry>Waiting for a read of a logical mapping during reorder buffer
management.</entry>
</row>
<row>
<entry><literal>ReplicationSlotRead</literal></entry>
<entry>Waiting for a read from a replication slot control file.</entry>
</row>
<row>
<entry><literal>ReplicationSlotRestoreSync</literal></entry>
<entry>Waiting for a replication slot control file to reach stable storage
while restoring it to memory.</entry>
</row>
<row>
<entry><literal>ReplicationSlotSync</literal></entry>
<entry>Waiting for a replication slot control file to reach stable
storage.</entry>
</row>
<row>
<entry><literal>ReplicationSlotWrite</literal></entry>
<entry>Waiting for a write to a replication slot control file.</entry>
</row>
<row>
<entry><literal>SLRUFlushSync</literal></entry>
<entry>Waiting for SLRU data to reach stable storage during a checkpoint
or database shutdown.</entry>
</row>
<row>
<entry><literal>SLRURead</literal></entry>
<entry>Waiting for a read of an SLRU page.</entry>
</row>
<row>
<entry><literal>SLRUSync</literal></entry>
<entry>Waiting for SLRU data to reach stable storage following a page
write.</entry>
</row>
<row>
<entry><literal>SLRUWrite</literal></entry>
<entry>Waiting for a write of an SLRU page.</entry>
</row>
<row>
<entry><literal>SnapbuildRead</literal></entry>
<entry>Waiting for a read of a serialized historical catalog
snapshot.</entry>
</row>
<row>
<entry><literal>SnapbuildSync</literal></entry>
<entry>Waiting for a serialized historical catalog snapshot to reach
stable storage.</entry>
</row>
<row>
<entry><literal>SnapbuildWrite</literal></entry>
<entry>Waiting for a write of a serialized historical catalog
snapshot.</entry>
</row>
<row>
<entry><literal>TimelineHistoryFileSync</literal></entry>
<entry>Waiting for a timeline history file received via streaming
replication to reach stable storage.</entry>
</row>
<row>
<entry><literal>TimelineHistoryFileWrite</literal></entry>
<entry>Waiting for a write of a timeline history file received via
streaming replication.</entry>
</row>
<row>
<entry><literal>TimelineHistoryRead</literal></entry>
<entry>Waiting for a read of a timeline history file.</entry>
</row>
<row>
<entry><literal>TimelineHistorySync</literal></entry>
<entry>Waiting for a newly created timeline history file to reach stable
storage.</entry>
</row>
<row>
<entry><literal>TimelineHistoryWrite</literal></entry>
<entry>Waiting for a write of a newly created timeline history
file.</entry>
</row>
<row>
<entry><literal>TwophaseFileRead</literal></entry>
<entry>Waiting for a read of a two phase state file.</entry>
</row>
<row>
<entry><literal>TwophaseFileSync</literal></entry>
<entry>Waiting for a two phase state file to reach stable storage.</entry>
</row>
<row>
<entry><literal>TwophaseFileWrite</literal></entry>
<entry>Waiting for a write of a two phase state file.</entry>
</row>
<row>
<entry><literal>WALBootstrapSync</literal></entry>
<entry>Waiting for WAL to reach stable storage during
bootstrapping.</entry>
</row>
<row>
<entry><literal>WALBootstrapWrite</literal></entry>
<entry>Waiting for a write of a WAL page during bootstrapping.</entry>
</row>
<row>
<entry><literal>WALCopyRead</literal></entry>
<entry>Waiting for a read when creating a new WAL segment by copying an
existing one.</entry>
</row>
<row>
<entry><literal>WALCopySync</literal></entry>
<entry>Waiting for a new WAL segment created by copying an existing one to
reach stable storage.</entry>
</row>
<row>
<entry><literal>WALCopyWrite</literal></entry>
<entry>Waiting for a write when creating a new WAL segment by copying an
existing one.</entry>
</row>
<row>
<entry><literal>WALInitSync</literal></entry>
<entry>Waiting for a newly initialized WAL file to reach stable
storage.</entry>
</row>
<row>
<entry><literal>WALInitWrite</literal></entry>
<entry>Waiting for a write while initializing a new WAL file.</entry>
</row>
<row>
<entry><literal>WALRead</literal></entry>
<entry>Waiting for a read from a WAL file.</entry>
</row>
<row>
<entry><literal>WALSenderTimelineHistoryRead</literal></entry>
<entry>Waiting for a read from a timeline history file during walsender
timeline command.</entry>
</row>
<row>
<entry><literal>WALSync</literal></entry>
<entry>Waiting for a WAL file to reach stable storage.</entry>
</row>
<row>
<entry><literal>WALSyncMethodAssign</literal></entry>
<entry>Waiting for data to reach stable storage while assigning WAL sync
method.</entry>
</row>
<row>
<entry><literal>WALWrite</literal></entry>
<entry>Waiting for a write to a WAL file.</entry>
</row>
</tbody>
</tgroup>
</table>
<table id="wait-event-ipc-table">
<title>Wait Events of Type <literal>IPC</literal></title>
<tgroup cols="2">
<thead>
<row>
<entry><literal>IPC</literal> Wait Event</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>BackupWaitWalArchive</literal></entry>
<entry>Waiting for WAL files required for the backup to be successfully
archived.</entry>
</row>
<row>
<entry><literal>BgWorkerShutdown</literal></entry>
<entry>Waiting for background worker to shut down.</entry>
</row>
<row>
<entry><literal>BgWorkerStartup</literal></entry>
<entry>Waiting for background worker to start up.</entry>
</row>
<row>
<entry><literal>BtreePage</literal></entry>
<entry>Waiting for the page number needed to continue a parallel B-tree
scan to become available.</entry>
</row>
<row>
<entry><literal>CheckpointDone</literal></entry>
<entry>Waiting for a checkpoint to complete.</entry>
</row>
<row>
<entry><literal>CheckpointStart</literal></entry>
<entry>Waiting for a checkpoint to start.</entry>
</row>
<row>
<entry><literal>ClogGroupUpdate</literal></entry>
<entry>Waiting for group leader to update transaction status at
transaction end.</entry>
</row>
<row>
<entry><literal>ExecuteGather</literal></entry>
<entry>Waiting for activity from child process while
executing <literal>Gather</literal> node.</entry>
</row>
<row>
<entry><literal>Hash/Batch/Allocating</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to allocate a hash
table.</entry>
</row>
<row>
<entry><literal>Hash/Batch/Electing</literal></entry>
<entry>Electing a Parallel Hash participant to allocate a hash table.</entry>
</row>
<row>
<entry><literal>Hash/Batch/Loading</literal></entry>
<entry>Waiting for other Parallel Hash participants to finish loading a
hash table.</entry>
</row>
<row>
<entry><literal>Hash/Build/Allocating</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to allocate the
initial hash table.</entry>
</row>
<row>
<entry><literal>Hash/Build/Electing</literal></entry>
<entry>Electing a Parallel Hash participant to allocate the initial hash table.</entry>
</row>
<row>
<entry><literal>Hash/Build/HashingInner</literal></entry>
<entry>Waiting for other Parallel Hash participants to finish hashing the
inner relation.</entry>
</row>
<row>
<entry><literal>Hash/Build/HashingOuter</literal></entry>
<entry>Waiting for other Parallel Hash participants to finish partitioning
the outer relation.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Allocating</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to allocate more
batches.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Deciding</literal></entry>
<entry>Electing a Parallel Hash participant to decide on future batch growth.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Electing</literal></entry>
<entry>Electing a Parallel Hash participant to allocate more batches.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Finishing</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to decide on
future batch growth.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Repartitioning</literal></entry>
<entry>Waiting for other Parallel Hash participants to finishing
repartitioning.</entry>
</row>
<row>
<entry><literal>Hash/GrowBuckets/Allocating</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to finish
allocating more buckets.</entry>
</row>
<row>
<entry><literal>Hash/GrowBuckets/Electing</literal></entry>
<entry>Electing a Parallel Hash participant to allocate more buckets.</entry>
</row>
<row>
<entry><literal>Hash/GrowBuckets/Reinserting</literal></entry>
<entry>Waiting for other Parallel Hash participants to finish inserting
tuples into new buckets.</entry>
</row>
<row>
<entry><literal>LogicalSyncData</literal></entry>
<entry>Waiting for logical replication remote server to send data for
initial table synchronization.</entry>
</row>
<row>
<entry><literal>LogicalSyncStateChange</literal></entry>
<entry>Waiting for logical replication remote server to change state.</entry>
</row>
<row>
<entry><literal>MessageQueueInternal</literal></entry>
<entry>Waiting for other process to be attached in shared message queue.</entry>
</row>
<row>
<entry><literal>MessageQueuePutMessage</literal></entry>
<entry>Waiting to write a protocol message to a shared message queue.</entry>
</row>
<row>
<entry><literal>MessageQueueReceive</literal></entry>
<entry>Waiting to receive bytes from a shared message queue.</entry>
</row>
<row>
<entry><literal>MessageQueueSend</literal></entry>
<entry>Waiting to send bytes to a shared message queue.</entry>
</row>
<row>
<entry><literal>ParallelBitmapScan</literal></entry>
<entry>Waiting for parallel bitmap scan to become initialized.</entry>
</row>
<row>
<entry><literal>ParallelCreateIndexScan</literal></entry>
<entry>Waiting for parallel <command>CREATE INDEX</command> workers to
finish heap scan.</entry>
</row>
<row>
<entry><literal>ParallelFinish</literal></entry>
<entry>Waiting for parallel workers to finish computing.</entry>
</row>
<row>
<entry><literal>ProcArrayGroupUpdate</literal></entry>
<entry>Waiting for group leader to clear transaction id at transaction end.</entry>
</row>
<row>
<entry><literal>Promote</literal></entry>
<entry>Waiting for standby promotion.</entry>
</row>
<row>
<entry><literal>RecoveryConflictSnapshot</literal></entry>
<entry>Waiting for recovery conflict resolution on a vacuum cleanup.</entry>
</row>
<row>
<entry><literal>RecoveryConflictTablespace</literal></entry>
<entry>Waiting for recovery conflict resolution on dropping tablespace.</entry>
</row>
<row>
<entry><literal>RecoveryPause</literal></entry>
<entry>Waiting for recovery to be resumed.</entry>
</row>
<row>
<entry><literal>ReplicationOriginDrop</literal></entry>
<entry>Waiting for a replication origin to become inactive to be dropped.</entry>
</row>
<row>
<entry><literal>ReplicationSlotDrop</literal></entry>
<entry>Waiting for a replication slot to become inactive to be dropped.</entry>
</row>
<row>
<entry><literal>SafeSnapshot</literal></entry>
<entry>Waiting for a snapshot for a <literal>READ ONLY DEFERRABLE</literal>
transaction.</entry>
</row>
<row>
<entry><literal>SyncRep</literal></entry>
<entry>Waiting for confirmation from remote server during synchronous
replication.</entry>
</row>
</tbody>
</tgroup>
</table>
<table id="wait-event-lock-table">
<title>Wait Events of Type <literal>Lock</literal></title>
<tgroup cols="2">
<thead>
<row>
<entry><literal>Lock</literal> Wait Event</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>advisory</literal></entry>
<entry>Waiting to acquire an advisory user lock.</entry>
</row>
<row>
<entry><literal>extend</literal></entry>
<entry>Waiting to extend a relation.</entry>
</row>
<row>
<entry><literal>object</literal></entry>
<entry>Waiting to acquire a lock on a non-relation database object.</entry>
</row>
<row>
<entry><literal>page</literal></entry>
<entry>Waiting to acquire a lock on page of a relation.</entry>
</row>
<row>
<entry><literal>relation</literal></entry>
<entry>Waiting to acquire a lock on a relation.</entry>
</row>
<row>
<entry><literal>speculative token</literal></entry>
<entry>Waiting to acquire a speculative insertion lock.</entry>
</row>
<row>
<entry><literal>transactionid</literal></entry>
<entry>Waiting for a transaction to finish.</entry>
</row>
<row>
<entry><literal>tuple</literal></entry>
<entry>Waiting to acquire a lock on a tuple.</entry>
</row>
<row>
<entry><literal>userlock</literal></entry>
<entry>Waiting to acquire a user lock.</entry>
</row>
<row>
<entry><literal>virtualxid</literal></entry>
<entry>Waiting to acquire a virtual xid lock.</entry>
</row>
</tbody>
</tgroup>
</table>
<table id="wait-event-lwlock-table">
<title>Wait Events of Type <literal>LWLock</literal></title>
<tgroup cols="2">
<thead>
<row>
<entry><literal>LWLock</literal> Wait Event</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>AddinShmemInitLock</literal></entry>
<entry>Waiting to manage space allocation in shared memory.</entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>state</structfield> <type>text</type>
</para>
<para>
Current overall state of this backend.
Possible values are:
<itemizedlist>
<listitem>
<para>
<literal>active</literal>: The backend is executing a query.
</para>
</listitem>
<listitem>
<para>
<literal>idle</literal>: The backend is waiting for a new client command.
</para>
</listitem>
<listitem>
<para>
<literal>idle in transaction</literal>: The backend is in a transaction,
but is not currently executing a query.
</para>
</listitem>
<listitem>
<para>
<literal>idle in transaction (aborted)</literal>: This state is similar to
<literal>idle in transaction</literal>, except one of the statements in
the transaction caused an error.
</para>
</listitem>
<listitem>
<para>
<literal>fastpath function call</literal>: The backend is executing a
fast-path function.
</para>
</listitem>
<listitem>
<para>
<literal>disabled</literal>: This state is reported if <xref linkend="guc-track-activities"/> is disabled in this backend.
</para>
</listitem>
</itemizedlist>
</para></entry>
<entry><literal>AsyncCtlLock</literal></entry>
<entry>Waiting to read or update shared notification state.</entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>backend_xid</structfield> <type>xid</type>
</para>
<para>
Top-level transaction identifier of this backend, if any.
</para></entry>
<entry><literal>AsyncQueueLock</literal></entry>
<entry>Waiting to read or update notification messages.</entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>backend_xmin</structfield> <type>xid</type>
</para>
<para>
The current backend's <literal>xmin</literal> horizon.
</para></entry>
<entry><literal>AutoFileLock</literal></entry>
<entry>Waiting to update the <filename>postgresql.auto.conf</filename> file.</entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>query</structfield> <type>text</type>
</para>
<para>
Text of this backend's most recent query. If
<structfield>state</structfield> is <literal>active</literal> 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
characters; this value can be changed via the parameter
<xref linkend="guc-track-activity-query-size"/>.
</para></entry>
<entry><literal>AutovacuumLock</literal></entry>
<entry>Autovacuum worker or launcher waiting to update or
read the current state of autovacuum workers.</entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>backend_type</structfield> <type>text</type>
</para>
<para>
Type of current backend. Possible types are
<literal>autovacuum launcher</literal>, <literal>autovacuum worker</literal>,
<literal>logical replication launcher</literal>,
<literal>logical replication worker</literal>,
<literal>parallel worker</literal>, <literal>background writer</literal>,
<literal>client backend</literal>, <literal>checkpointer</literal>,
<literal>startup</literal>, <literal>walreceiver</literal>,
<literal>walsender</literal> and <literal>walwriter</literal>.
In addition, background workers registered by extensions may have
additional types.
</para></entry>
<entry><literal>AutovacuumScheduleLock</literal></entry>
<entry>Waiting to ensure that the table selected for a vacuum
still needs vacuuming.</entry>
</row>
<row>
<entry><literal>BackgroundWorkerLock</literal></entry>
<entry>Waiting to read or update background worker state.</entry>
</row>
<row>
<entry><literal>BtreeVacuumLock</literal></entry>
<entry>Waiting to read or update vacuum-related information for a
B-tree index.</entry>
</row>
<row>
<entry><literal>CLogControlLock</literal></entry>
<entry>Waiting to read or update transaction status.</entry>
</row>
<row>
<entry><literal>CLogTruncationLock</literal></entry>
<entry>Waiting to execute <function>pg_xact_status</function> or update
the oldest transaction id available to it.</entry>
</row>
<row>
<entry><literal>CheckpointLock</literal></entry>
<entry>Waiting to perform checkpoint.</entry>
</row>
<row>
<entry><literal>CheckpointerCommLock</literal></entry>
<entry>Waiting to manage fsync requests.</entry>
</row>
<row>
<entry><literal>CommitTsControlLock</literal></entry>
<entry>Waiting to read or update transaction commit timestamps.</entry>
</row>
<row>
<entry><literal>CommitTsLock</literal></entry>
<entry>Waiting to read or update the last value set for the
transaction timestamp.</entry>
</row>
<row>
<entry><literal>ControlFileLock</literal></entry>
<entry>Waiting to read or update the control file or creation of a
new WAL file.</entry>
</row>
<row>
<entry><literal>DynamicSharedMemoryControlLock</literal></entry>
<entry>Waiting to read or update dynamic shared memory state.</entry>
</row>
<row>
<entry><literal>LogicalRepWorkerLock</literal></entry>
<entry>Waiting for action on logical replication worker to finish.</entry>
</row>
<row>
<entry><literal>MultiXactGenLock</literal></entry>
<entry>Waiting to read or update shared multixact state.</entry>
</row>
<row>
<entry><literal>MultiXactMemberControlLock</literal></entry>
<entry>Waiting to read or update multixact member mappings.</entry>
</row>
<row>
<entry><literal>MultiXactOffsetControlLock</literal></entry>
<entry>Waiting to read or update multixact offset mappings.</entry>
</row>
<row>
<entry><literal>MultiXactTruncationLock</literal></entry>
<entry>Waiting to read or truncate multixact information.</entry>
</row>
<row>
<entry><literal>OidGenLock</literal></entry>
<entry>Waiting to allocate or assign an OID.</entry>
</row>
<row>
<entry><literal>OldSerXidLock</literal></entry>
<entry>Waiting to read or record conflicting serializable
transactions.</entry>
</row>
<row>
<entry><literal>OldSnapshotTimeMapLock</literal></entry>
<entry>Waiting to read or update old snapshot control information.</entry>
</row>
<row>
<entry><literal>ProcArrayLock</literal></entry>
<entry>Waiting to get a snapshot or clearing a transaction id at
transaction end.</entry>
</row>
<row>
<entry><literal>RelCacheInitLock</literal></entry>
<entry>Waiting to read or write relation cache initialization file.</entry>
</row>
<row>
<entry><literal>RelationMappingLock</literal></entry>
<entry>Waiting to update the relation map file used to store catalog
to filenode mapping.</entry>
</row>
<row>
<entry><literal>ReplicationOriginLock</literal></entry>
<entry>Waiting to setup, drop or use replication origin.</entry>
</row>
<row>
<entry><literal>ReplicationSlotAllocationLock</literal></entry>
<entry>Waiting to allocate or free a replication slot.</entry>
</row>
<row>
<entry><literal>ReplicationSlotControlLock</literal></entry>
<entry>Waiting to read or update replication slot state.</entry>
</row>
<row>
<entry><literal>SInvalReadLock</literal></entry>
<entry>Waiting to retrieve or remove messages from shared invalidation
queue.</entry>
</row>
<row>
<entry><literal>SInvalWriteLock</literal></entry>
<entry>Waiting to add a message in shared invalidation queue.</entry>
</row>
<row>
<entry><literal>SerializableFinishedListLock</literal></entry>
<entry>Waiting to access the list of finished serializable
transactions.</entry>
</row>
<row>
<entry><literal>SerializablePredicateLockListLock</literal></entry>
<entry>Waiting to perform an operation on a list of locks held by
serializable transactions.</entry>
</row>
<row>
<entry><literal>SerializableXactHashLock</literal></entry>
<entry>Waiting to retrieve or store information about serializable
transactions.</entry>
</row>
<row>
<entry><literal>ShmemIndexLock</literal></entry>
<entry>Waiting to find or allocate space in shared memory.</entry>
</row>
<row>
<entry><literal>SubtransControlLock</literal></entry>
<entry>Waiting to read or update sub-transaction information.</entry>
</row>
<row>
<entry><literal>SyncRepLock</literal></entry>
<entry>Waiting to read or update information about synchronous
replicas.</entry>
</row>
<row>
<entry><literal>SyncScanLock</literal></entry>
<entry>Waiting to get the start location of a scan on a table for
synchronized scans.</entry>
</row>
<row>
<entry><literal>TablespaceCreateLock</literal></entry>
<entry>Waiting to create or drop the tablespace.</entry>
</row>
<row>
<entry><literal>TwoPhaseStateLock</literal></entry>
<entry>Waiting to read or update the state of prepared transactions.</entry>
</row>
<row>
<entry><literal>WALBufMappingLock</literal></entry>
<entry>Waiting to replace a page in WAL buffers.</entry>
</row>
<row>
<entry><literal>WALWriteLock</literal></entry>
<entry>Waiting for WAL buffers to be written to disk.</entry>
</row>
<row>
<entry><literal>XidGenLock</literal></entry>
<entry>Waiting to allocate or assign a transaction id.</entry>
</row>
<row>
<entry><literal>async</literal></entry>
<entry>Waiting for I/O on an async (notify) buffer.</entry>
</row>
<row>
<entry><literal>buffer_content</literal></entry>
<entry>Waiting to read or write a data page in memory.</entry>
</row>
<row>
<entry><literal>buffer_io</literal></entry>
<entry>Waiting for I/O on a data page.</entry>
</row>
<row>
<entry><literal>buffer_mapping</literal></entry>
<entry>Waiting to associate a data block with a buffer in the buffer
pool.</entry>
</row>
<row>
<entry><literal>clog</literal></entry>
<entry>Waiting for I/O on a clog (transaction status) buffer.</entry>
</row>
<row>
<entry><literal>commit_timestamp</literal></entry>
<entry>Waiting for I/O on commit timestamp buffer.</entry>
</row>
<row>
<entry><literal>lock_manager</literal></entry>
<entry>Waiting to add or examine locks for backends, or waiting to
join or exit a locking group (used by parallel query).</entry>
</row>
<row>
<entry><literal>multixact_member</literal></entry>
<entry>Waiting for I/O on a multixact_member buffer.</entry>
</row>
<row>
<entry><literal>multixact_offset</literal></entry>
<entry>Waiting for I/O on a multixact offset buffer.</entry>
</row>
<row>
<entry><literal>oldserxid</literal></entry>
<entry>Waiting for I/O on an oldserxid buffer.</entry>
</row>
<row>
<entry><literal>parallel_append</literal></entry>
<entry>Waiting to choose the next subplan during Parallel Append plan
execution.</entry>
</row>
<row>
<entry><literal>parallel_hash_join</literal></entry>
<entry>Waiting to allocate or exchange a chunk of memory or update
counters during Parallel Hash plan execution.</entry>
</row>
<row>
<entry><literal>parallel_query_dsa</literal></entry>
<entry>Waiting for parallel query dynamic shared memory allocation lock.</entry>
</row>
<row>
<entry><literal>predicate_lock_manager</literal></entry>
<entry>Waiting to add or examine predicate lock information.</entry>
</row>
<row>
<entry><literal>proc</literal></entry>
<entry>Waiting to read or update the fast-path lock information.</entry>
</row>
<row>
<entry><literal>replication_origin</literal></entry>
<entry>Waiting to read or update the replication progress.</entry>
</row>
<row>
<entry><literal>replication_slot_io</literal></entry>
<entry>Waiting for I/O on a replication slot.</entry>
</row>
<row>
<entry><literal>serializable_xact</literal></entry>
<entry>Waiting to perform an operation on a serializable transaction
in a parallel query.</entry>
</row>
<row>
<entry><literal>subtrans</literal></entry>
<entry>Waiting for I/O on a subtransaction buffer.</entry>
</row>
<row>
<entry><literal>tbm</literal></entry>
<entry>Waiting for TBM shared iterator lock.</entry>
</row>
<row>
<entry><literal>wal_insert</literal></entry>
<entry>Waiting to insert WAL into a memory buffer.</entry>
</row>
</tbody>
</tgroup>
</table>
<para>
The <structname>pg_stat_activity</structname> view will have one row
per server process, showing information related to
the current activity of that process.
</para>
<note>
<para>
The <structfield>wait_event</structfield> and <structfield>state</structfield> columns are
independent. If a backend is in the <literal>active</literal> state,
it may or may not be <literal>waiting</literal> on some event. If the state
is <literal>active</literal> and <structfield>wait_event</structfield> is non-null, it
means that a query is being executed, but is being blocked somewhere
in the system.
</para>
</note>
<table id="wait-event-table">
<title><structname>wait_event</structname> Description</title>
<tgroup cols="3">
<thead>
<row>
<entry>Wait Event Type</entry>
<entry>Wait Event Name</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry morerows="64"><literal>LWLock</literal></entry>
<entry><literal>ShmemIndexLock</literal></entry>
<entry>Waiting to find or allocate space in shared memory.</entry>
</row>
<row>
<entry><literal>OidGenLock</literal></entry>
<entry>Waiting to allocate or assign an OID.</entry>
</row>
<row>
<entry><literal>XidGenLock</literal></entry>
<entry>Waiting to allocate or assign a transaction id.</entry>
</row>
<row>
<entry><literal>ProcArrayLock</literal></entry>
<entry>Waiting to get a snapshot or clearing a transaction id at
transaction end.</entry>
</row>
<row>
<entry><literal>SInvalReadLock</literal></entry>
<entry>Waiting to retrieve or remove messages from shared invalidation
queue.</entry>
</row>
<row>
<entry><literal>SInvalWriteLock</literal></entry>
<entry>Waiting to add a message in shared invalidation queue.</entry>
</row>
<row>
<entry><literal>WALBufMappingLock</literal></entry>
<entry>Waiting to replace a page in WAL buffers.</entry>
</row>
<row>
<entry><literal>WALWriteLock</literal></entry>
<entry>Waiting for WAL buffers to be written to disk.</entry>
</row>
<row>
<entry><literal>ControlFileLock</literal></entry>
<entry>Waiting to read or update the control file or creation of a
new WAL file.</entry>
</row>
<row>
<entry><literal>CheckpointLock</literal></entry>
<entry>Waiting to perform checkpoint.</entry>
</row>
<row>
<entry><literal>CLogControlLock</literal></entry>
<entry>Waiting to read or update transaction status.</entry>
</row>
<row>
<entry><literal>SubtransControlLock</literal></entry>
<entry>Waiting to read or update sub-transaction information.</entry>
</row>
<row>
<entry><literal>MultiXactGenLock</literal></entry>
<entry>Waiting to read or update shared multixact state.</entry>
</row>
<row>
<entry><literal>MultiXactOffsetControlLock</literal></entry>
<entry>Waiting to read or update multixact offset mappings.</entry>
</row>
<row>
<entry><literal>MultiXactMemberControlLock</literal></entry>
<entry>Waiting to read or update multixact member mappings.</entry>
</row>
<row>
<entry><literal>RelCacheInitLock</literal></entry>
<entry>Waiting to read or write relation cache initialization
file.</entry>
</row>
<row>
<entry><literal>CheckpointerCommLock</literal></entry>
<entry>Waiting to manage fsync requests.</entry>
</row>
<row>
<entry><literal>TwoPhaseStateLock</literal></entry>
<entry>Waiting to read or update the state of prepared transactions.</entry>
</row>
<row>
<entry><literal>TablespaceCreateLock</literal></entry>
<entry>Waiting to create or drop the tablespace.</entry>
</row>
<row>
<entry><literal>BtreeVacuumLock</literal></entry>
<entry>Waiting to read or update vacuum-related information for a
B-tree index.</entry>
</row>
<row>
<entry><literal>AddinShmemInitLock</literal></entry>
<entry>Waiting to manage space allocation in shared memory.</entry>
</row>
<row>
<entry><literal>AutovacuumLock</literal></entry>
<entry>Autovacuum worker or launcher waiting to update or
read the current state of autovacuum workers.</entry>
</row>
<row>
<entry><literal>AutovacuumScheduleLock</literal></entry>
<entry>Waiting to ensure that the table it has selected for a vacuum
still needs vacuuming.
</entry>
</row>
<row>
<entry><literal>SyncScanLock</literal></entry>
<entry>Waiting to get the start location of a scan on a table for
synchronized scans.</entry>
</row>
<row>
<entry><literal>RelationMappingLock</literal></entry>
<entry>Waiting to update the relation map file used to store catalog
to filenode mapping.
</entry>
</row>
<row>
<entry><literal>AsyncCtlLock</literal></entry>
<entry>Waiting to read or update shared notification state.</entry>
</row>
<row>
<entry><literal>AsyncQueueLock</literal></entry>
<entry>Waiting to read or update notification messages.</entry>
</row>
<row>
<entry><literal>SerializableXactHashLock</literal></entry>
<entry>Waiting to retrieve or store information about serializable
transactions.</entry>
</row>
<row>
<entry><literal>SerializableFinishedListLock</literal></entry>
<entry>Waiting to access the list of finished serializable
transactions.</entry>
</row>
<row>
<entry><literal>SerializablePredicateLockListLock</literal></entry>
<entry>Waiting to perform an operation on a list of locks held by
serializable transactions.</entry>
</row>
<row>
<entry><literal>OldSerXidLock</literal></entry>
<entry>Waiting to read or record conflicting serializable
transactions.</entry>
</row>
<row>
<entry><literal>SyncRepLock</literal></entry>
<entry>Waiting to read or update information about synchronous
replicas.</entry>
</row>
<row>
<entry><literal>BackgroundWorkerLock</literal></entry>
<entry>Waiting to read or update background worker state.</entry>
</row>
<row>
<entry><literal>DynamicSharedMemoryControlLock</literal></entry>
<entry>Waiting to read or update dynamic shared memory state.</entry>
</row>
<row>
<entry><literal>AutoFileLock</literal></entry>
<entry>Waiting to update the <filename>postgresql.auto.conf</filename> file.</entry>
</row>
<row>
<entry><literal>ReplicationSlotAllocationLock</literal></entry>
<entry>Waiting to allocate or free a replication slot.</entry>
</row>
<row>
<entry><literal>ReplicationSlotControlLock</literal></entry>
<entry>Waiting to read or update replication slot state.</entry>
</row>
<row>
<entry><literal>CommitTsControlLock</literal></entry>
<entry>Waiting to read or update transaction commit timestamps.</entry>
</row>
<row>
<entry><literal>CommitTsLock</literal></entry>
<entry>Waiting to read or update the last value set for the
transaction timestamp.</entry>
</row>
<row>
<entry><literal>ReplicationOriginLock</literal></entry>
<entry>Waiting to setup, drop or use replication origin.</entry>
</row>
<row>
<entry><literal>MultiXactTruncationLock</literal></entry>
<entry>Waiting to read or truncate multixact information.</entry>
</row>
<row>
<entry><literal>OldSnapshotTimeMapLock</literal></entry>
<entry>Waiting to read or update old snapshot control information.</entry>
</row>
<row>
<entry><literal>LogicalRepWorkerLock</literal></entry>
<entry>Waiting for action on logical replication worker to finish.</entry>
</row>
<row>
<entry><literal>CLogTruncationLock</literal></entry>
<entry>Waiting to execute <function>pg_xact_status</function> or update
the oldest transaction id available to it.</entry>
</row>
<row>
<entry><literal>clog</literal></entry>
<entry>Waiting for I/O on a clog (transaction status) buffer.</entry>
</row>
<row>
<entry><literal>commit_timestamp</literal></entry>
<entry>Waiting for I/O on commit timestamp buffer.</entry>
</row>
<row>
<entry><literal>subtrans</literal></entry>
<entry>Waiting for I/O a subtransaction buffer.</entry>
</row>
<row>
<entry><literal>multixact_offset</literal></entry>
<entry>Waiting for I/O on a multixact offset buffer.</entry>
</row>
<row>
<entry><literal>multixact_member</literal></entry>
<entry>Waiting for I/O on a multixact_member buffer.</entry>
</row>
<row>
<entry><literal>async</literal></entry>
<entry>Waiting for I/O on an async (notify) buffer.</entry>
</row>
<row>
<entry><literal>oldserxid</literal></entry>
<entry>Waiting for I/O on an oldserxid buffer.</entry>
</row>
<row>
<entry><literal>wal_insert</literal></entry>
<entry>Waiting to insert WAL into a memory buffer.</entry>
</row>
<row>
<entry><literal>buffer_content</literal></entry>
<entry>Waiting to read or write a data page in memory.</entry>
</row>
<row>
<entry><literal>buffer_io</literal></entry>
<entry>Waiting for I/O on a data page.</entry>
</row>
<row>
<entry><literal>replication_origin</literal></entry>
<entry>Waiting to read or update the replication progress.</entry>
</row>
<row>
<entry><literal>replication_slot_io</literal></entry>
<entry>Waiting for I/O on a replication slot.</entry>
</row>
<row>
<entry><literal>proc</literal></entry>
<entry>Waiting to read or update the fast-path lock information.</entry>
</row>
<row>
<entry><literal>buffer_mapping</literal></entry>
<entry>Waiting to associate a data block with a buffer in the buffer
pool.</entry>
</row>
<row>
<entry><literal>lock_manager</literal></entry>
<entry>Waiting to add or examine locks for backends, or waiting to
join or exit a locking group (used by parallel query).</entry>
</row>
<row>
<entry><literal>predicate_lock_manager</literal></entry>
<entry>Waiting to add or examine predicate lock information.</entry>
</row>
<row>
<entry><literal>serializable_xact</literal></entry>
<entry>Waiting to perform an operation on a serializable transaction
in a parallel query.</entry>
</row>
<row>
<entry><literal>parallel_query_dsa</literal></entry>
<entry>Waiting for parallel query dynamic shared memory allocation lock.</entry>
</row>
<row>
<entry><literal>tbm</literal></entry>
<entry>Waiting for TBM shared iterator lock.</entry>
</row>
<row>
<entry><literal>parallel_append</literal></entry>
<entry>Waiting to choose the next subplan during Parallel Append plan
execution.</entry>
</row>
<row>
<entry><literal>parallel_hash_join</literal></entry>
<entry>Waiting to allocate or exchange a chunk of memory or update
counters during Parallel Hash plan execution.</entry>
</row>
<row>
<entry morerows="9"><literal>Lock</literal></entry>
<entry><literal>relation</literal></entry>
<entry>Waiting to acquire a lock on a relation.</entry>
</row>
<row>
<entry><literal>extend</literal></entry>
<entry>Waiting to extend a relation.</entry>
</row>
<row>
<entry><literal>page</literal></entry>
<entry>Waiting to acquire a lock on page of a relation.</entry>
</row>
<row>
<entry><literal>tuple</literal></entry>
<entry>Waiting to acquire a lock on a tuple.</entry>
</row>
<row>
<entry><literal>transactionid</literal></entry>
<entry>Waiting for a transaction to finish.</entry>
</row>
<row>
<entry><literal>virtualxid</literal></entry>
<entry>Waiting to acquire a virtual xid lock.</entry>
</row>
<row>
<entry><literal>speculative token</literal></entry>
<entry>Waiting to acquire a speculative insertion lock.</entry>
</row>
<row>
<entry><literal>object</literal></entry>
<entry>Waiting to acquire a lock on a non-relation database object.</entry>
</row>
<row>
<entry><literal>userlock</literal></entry>
<entry>Waiting to acquire a user lock.</entry>
</row>
<row>
<entry><literal>advisory</literal></entry>
<entry>Waiting to acquire an advisory user lock.</entry>
</row>
<row>
<entry><literal>BufferPin</literal></entry>
<entry><literal>BufferPin</literal></entry>
<entry>Waiting to acquire a pin on a buffer.</entry>
</row>
<row>
<entry morerows="12"><literal>Activity</literal></entry>
<entry><literal>ArchiverMain</literal></entry>
<entry>Waiting in main loop of the archiver process.</entry>
</row>
<row>
<entry><literal>AutoVacuumMain</literal></entry>
<entry>Waiting in main loop of autovacuum launcher process.</entry>
</row>
<row>
<entry><literal>BgWriterHibernate</literal></entry>
<entry>Waiting in background writer process, hibernating.</entry>
</row>
<row>
<entry><literal>BgWriterMain</literal></entry>
<entry>Waiting in main loop of background writer process background worker.</entry>
</row>
<row>
<entry><literal>CheckpointerMain</literal></entry>
<entry>Waiting in main loop of checkpointer process.</entry>
</row>
<row>
<entry><literal>LogicalApplyMain</literal></entry>
<entry>Waiting in main loop of logical apply process.</entry>
</row>
<row>
<entry><literal>LogicalLauncherMain</literal></entry>
<entry>Waiting in main loop of logical launcher process.</entry>
</row>
<row>
<entry><literal>PgStatMain</literal></entry>
<entry>Waiting in main loop of the statistics collector process.</entry>
</row>
<row>
<entry><literal>RecoveryWalStream</literal></entry>
<entry>Waiting for WAL from a stream at recovery.</entry>
</row>
<row>
<entry><literal>SysLoggerMain</literal></entry>
<entry>Waiting in main loop of syslogger process.</entry>
</row>
<row>
<entry><literal>WalReceiverMain</literal></entry>
<entry>Waiting in main loop of WAL receiver process.</entry>
</row>
<row>
<entry><literal>WalSenderMain</literal></entry>
<entry>Waiting in main loop of WAL sender process.</entry>
</row>
<row>
<entry><literal>WalWriterMain</literal></entry>
<entry>Waiting in main loop of WAL writer process.</entry>
</row>
<row>
<entry morerows="8"><literal>Client</literal></entry>
<entry><literal>ClientRead</literal></entry>
<entry>Waiting to read data from the client.</entry>
</row>
<row>
<entry><literal>ClientWrite</literal></entry>
<entry>Waiting to write data to the client.</entry>
</row>
<row>
<entry><literal>GSSOpenServer</literal></entry>
<entry>Waiting to read data from the client while establishing the GSSAPI session.</entry>
</row>
<row>
<entry><literal>LibPQWalReceiverConnect</literal></entry>
<entry>Waiting in WAL receiver to establish connection to remote server.</entry>
</row>
<row>
<entry><literal>LibPQWalReceiverReceive</literal></entry>
<entry>Waiting in WAL receiver to receive data from remote server.</entry>
</row>
<row>
<entry><literal>SSLOpenServer</literal></entry>
<entry>Waiting for SSL while attempting connection.</entry>
</row>
<row>
<entry><literal>WalReceiverWaitStart</literal></entry>
<entry>Waiting for startup process to send initial data for streaming replication.</entry>
</row>
<row>
<entry><literal>WalSenderWaitForWAL</literal></entry>
<entry>Waiting for WAL to be flushed in WAL sender process.</entry>
</row>
<row>
<entry><literal>WalSenderWriteData</literal></entry>
<entry>Waiting for any activity when processing replies from WAL receiver in WAL sender process.</entry>
</row>
<row>
<entry><literal>Extension</literal></entry>
<entry><literal>Extension</literal></entry>
<entry>Waiting in an extension.</entry>
</row>
<row>
<entry morerows="40"><literal>IPC</literal></entry>
<entry><literal>BackupWaitWalArchive</literal></entry>
<entry>Waiting for WAL files required for the backup to be successfully archived.</entry>
</row>
<row>
<entry><literal>BgWorkerShutdown</literal></entry>
<entry>Waiting for background worker to shut down.</entry>
</row>
<row>
<entry><literal>BgWorkerStartup</literal></entry>
<entry>Waiting for background worker to start up.</entry>
</row>
<row>
<entry><literal>BtreePage</literal></entry>
<entry>Waiting for the page number needed to continue a parallel B-tree scan to become available.</entry>
</row>
<row>
<entry><literal>CheckpointDone</literal></entry>
<entry>Waiting for a checkpoint to complete.</entry>
</row>
<row>
<entry><literal>CheckpointStart</literal></entry>
<entry>Waiting for a checkpoint to start.</entry>
</row>
<row>
<entry><literal>ClogGroupUpdate</literal></entry>
<entry>Waiting for group leader to update transaction status at transaction end.</entry>
</row>
<row>
<entry><literal>ExecuteGather</literal></entry>
<entry>Waiting for activity from child process when executing <literal>Gather</literal> node.</entry>
</row>
<row>
<entry><literal>Hash/Batch/Allocating</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to allocate a hash table.</entry>
</row>
<row>
<entry><literal>Hash/Batch/Electing</literal></entry>
<entry>Electing a Parallel Hash participant to allocate a hash table.</entry>
</row>
<row>
<entry><literal>Hash/Batch/Loading</literal></entry>
<entry>Waiting for other Parallel Hash participants to finish loading a hash table.</entry>
</row>
<row>
<entry><literal>Hash/Build/Allocating</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to allocate the initial hash table.</entry>
</row>
<row>
<entry><literal>Hash/Build/Electing</literal></entry>
<entry>Electing a Parallel Hash participant to allocate the initial hash table.</entry>
</row>
<row>
<entry><literal>Hash/Build/HashingInner</literal></entry>
<entry>Waiting for other Parallel Hash participants to finish hashing the inner relation.</entry>
</row>
<row>
<entry><literal>Hash/Build/HashingOuter</literal></entry>
<entry>Waiting for other Parallel Hash participants to finish partitioning the outer relation.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Allocating</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to allocate more batches.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Deciding</literal></entry>
<entry>Electing a Parallel Hash participant to decide on future batch growth.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Electing</literal></entry>
<entry>Electing a Parallel Hash participant to allocate more batches.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Finishing</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to decide on future batch growth.</entry>
</row>
<row>
<entry><literal>Hash/GrowBatches/Repartitioning</literal></entry>
<entry>Waiting for other Parallel Hash participants to finishing repartitioning.</entry>
</row>
<row>
<entry><literal>Hash/GrowBuckets/Allocating</literal></entry>
<entry>Waiting for an elected Parallel Hash participant to finish allocating more buckets.</entry>
</row>
<row>
<entry><literal>Hash/GrowBuckets/Electing</literal></entry>
<entry>Electing a Parallel Hash participant to allocate more buckets.</entry>
</row>
<row>
<entry><literal>Hash/GrowBuckets/Reinserting</literal></entry>
<entry>Waiting for other Parallel Hash participants to finish inserting tuples into new buckets.</entry>
</row>
<row>
<entry><literal>LogicalSyncData</literal></entry>
<entry>Waiting for logical replication remote server to send data for initial table synchronization.</entry>
</row>
<row>
<entry><literal>LogicalSyncStateChange</literal></entry>
<entry>Waiting for logical replication remote server to change state.</entry>
</row>
<row>
<entry><literal>MessageQueueInternal</literal></entry>
<entry>Waiting for other process to be attached in shared message queue.</entry>
</row>
<row>
<entry><literal>MessageQueuePutMessage</literal></entry>
<entry>Waiting to write a protocol message to a shared message queue.</entry>
</row>
<row>
<entry><literal>MessageQueueReceive</literal></entry>
<entry>Waiting to receive bytes from a shared message queue.</entry>
</row>
<row>
<entry><literal>MessageQueueSend</literal></entry>
<entry>Waiting to send bytes to a shared message queue.</entry>
</row>
<row>
<entry><literal>ParallelBitmapScan</literal></entry>
<entry>Waiting for parallel bitmap scan to become initialized.</entry>
</row>
<row>
<entry><literal>ParallelCreateIndexScan</literal></entry>
<entry>Waiting for parallel <command>CREATE INDEX</command> workers to finish heap scan.</entry>
</row>
<row>
<entry><literal>ParallelFinish</literal></entry>
<entry>Waiting for parallel workers to finish computing.</entry>
</row>
<row>
<entry><literal>ProcArrayGroupUpdate</literal></entry>
<entry>Waiting for group leader to clear transaction id at transaction end.</entry>
</row>
<row>
<entry><literal>Promote</literal></entry>
<entry>Waiting for standby promotion.</entry>
</row>
<row>
<entry><literal>RecoveryConflictSnapshot</literal></entry>
<entry>Waiting for recovery conflict resolution on a vacuum cleanup.</entry>
</row>
<row>
<entry><literal>RecoveryConflictTablespace</literal></entry>
<entry>Waiting for recovery conflict resolution on dropping tablespace.</entry>
</row>
<row>
<entry><literal>RecoveryPause</literal></entry>
<entry>Waiting for recovery to be resumed.</entry>
</row>
<row>
<entry><literal>ReplicationOriginDrop</literal></entry>
<entry>Waiting for a replication origin to become inactive to be dropped.</entry>
</row>
<row>
<entry><literal>ReplicationSlotDrop</literal></entry>
<entry>Waiting for a replication slot to become inactive to be dropped.</entry>
</row>
<row>
<entry><literal>SafeSnapshot</literal></entry>
<entry>Waiting for a snapshot for a <literal>READ ONLY DEFERRABLE</literal> transaction.</entry>
</row>
<row>
<entry><literal>SyncRep</literal></entry>
<entry>Waiting for confirmation from remote server during synchronous replication.</entry>
</row>
<row>
<entry morerows="4"><literal>Timeout</literal></entry>
<entry><literal>BaseBackupThrottle</literal></entry>
<entry>Waiting during base backup when throttling activity.</entry>
</row>
<row>
<entry><literal>PgSleep</literal></entry>
<entry>Waiting in process that called <function>pg_sleep</function>.</entry>
</row>
<row>
<entry><literal>RecoveryApplyDelay</literal></entry>
<entry>Waiting to apply WAL at recovery because it is delayed.</entry>
</row>
<row>
<entry><literal>RecoveryRetrieveRetryInterval</literal></entry>
<entry>
Waiting when WAL data is not available from any kind of sources
(<filename>pg_wal</filename>, archive or stream) before trying
again to retrieve WAL data, at recovery.
</entry>
</row>
<row>
<entry><literal>VacuumDelay</literal></entry>
<entry>Waiting in a cost-based vacuum delay point.</entry>
</row>
<row>
<entry morerows="68"><literal>IO</literal></entry>
<entry><literal>BufFileRead</literal></entry>
<entry>Waiting for a read from a buffered file.</entry>
</row>
<row>
<entry><literal>BufFileWrite</literal></entry>
<entry>Waiting for a write to a buffered file.</entry>
</row>
<row>
<entry><literal>ControlFileRead</literal></entry>
<entry>Waiting for a read from the control file.</entry>
</row>
<row>
<entry><literal>ControlFileSync</literal></entry>
<entry>Waiting for the control file to reach stable storage.</entry>
</row>
<row>
<entry><literal>ControlFileSyncUpdate</literal></entry>
<entry>Waiting for an update to the control file to reach stable storage.</entry>
</row>
<row>
<entry><literal>ControlFileWrite</literal></entry>
<entry>Waiting for a write to the control file.</entry>
</row>
<row>
<entry><literal>ControlFileWriteUpdate</literal></entry>
<entry>Waiting for a write to update the control file.</entry>
</row>
<row>
<entry><literal>CopyFileRead</literal></entry>
<entry>Waiting for a read during a file copy operation.</entry>
</row>
<row>
<entry><literal>CopyFileWrite</literal></entry>
<entry>Waiting for a write during a file copy operation.</entry>
</row>
<row>
<entry><literal>DataFileExtend</literal></entry>
<entry>Waiting for a relation data file to be extended.</entry>
</row>
<row>
<entry><literal>DataFileFlush</literal></entry>
<entry>Waiting for a relation data file to reach stable storage.</entry>
</row>
<row>
<entry><literal>DataFileImmediateSync</literal></entry>
<entry>Waiting for an immediate synchronization of a relation data file to stable storage.</entry>
</row>
<row>
<entry><literal>DataFilePrefetch</literal></entry>
<entry>Waiting for an asynchronous prefetch from a relation data file.</entry>
</row>
<row>
<entry><literal>DataFileRead</literal></entry>
<entry>Waiting for a read from a relation data file.</entry>
</row>
<row>
<entry><literal>DataFileSync</literal></entry>
<entry>Waiting for changes to a relation data file to reach stable storage.</entry>
</row>
<row>
<entry><literal>DataFileTruncate</literal></entry>
<entry>Waiting for a relation data file to be truncated.</entry>
</row>
<row>
<entry><literal>DataFileWrite</literal></entry>
<entry>Waiting for a write to a relation data file.</entry>
</row>
<row>
<entry><literal>DSMFillZeroWrite</literal></entry>
<entry>Waiting to write zero bytes to a dynamic shared memory backing file.</entry>
</row>
<row>
<entry><literal>LockFileAddToDataDirRead</literal></entry>
<entry>Waiting for a read while adding a line to the data directory lock file.</entry>
</row>
<row>
<entry><literal>LockFileAddToDataDirSync</literal></entry>
<entry>Waiting for data to reach stable storage while adding a line to the data directory lock file.</entry>
</row>
<row>
<entry><literal>LockFileAddToDataDirWrite</literal></entry>
<entry>Waiting for a write while adding a line to the data directory lock file.</entry>
</row>
<row>
<entry><literal>LockFileCreateRead</literal></entry>
<entry>Waiting to read while creating the data directory lock file.</entry>
</row>
<row>
<entry><literal>LockFileCreateSync</literal></entry>
<entry>Waiting for data to reach stable storage while creating the data directory lock file.</entry>
</row>
<row>
<entry><literal>LockFileCreateWrite</literal></entry>
<entry>Waiting for a write while creating the data directory lock file.</entry>
</row>
<row>
<entry><literal>LockFileReCheckDataDirRead</literal></entry>
<entry>Waiting for a read during recheck of the data directory lock file.</entry>
</row>
<row>
<entry><literal>LogicalRewriteCheckpointSync</literal></entry>
<entry>Waiting for logical rewrite mappings to reach stable storage during a checkpoint.</entry>
</row>
<row>
<entry><literal>LogicalRewriteMappingSync</literal></entry>
<entry>Waiting for mapping data to reach stable storage during a logical rewrite.</entry>
</row>
<row>
<entry><literal>LogicalRewriteMappingWrite</literal></entry>
<entry>Waiting for a write of mapping data during a logical rewrite.</entry>
</row>
<row>
<entry><literal>LogicalRewriteSync</literal></entry>
<entry>Waiting for logical rewrite mappings to reach stable storage.</entry>
</row>
<row>
<entry><literal>LogicalRewriteTruncate</literal></entry>
<entry>Waiting for truncate of mapping data during a logical rewrite.</entry>
</row>
<row>
<entry><literal>LogicalRewriteWrite</literal></entry>
<entry>Waiting for a write of logical rewrite mappings.</entry>
</row>
<row>
<entry><literal>ProcSignalBarrier</literal></entry>
<entry>Waiting for a barrier event to be processed by all backends.</entry>
</row>
<row>
<entry><literal>RelationMapRead</literal></entry>
<entry>Waiting for a read of the relation map file.</entry>
</row>
<row>
<entry><literal>RelationMapSync</literal></entry>
<entry>Waiting for the relation map file to reach stable storage.</entry>
</row>
<row>
<entry><literal>RelationMapWrite</literal></entry>
<entry>Waiting for a write to the relation map file.</entry>
</row>
<row>
<entry><literal>ReorderBufferRead</literal></entry>
<entry>Waiting for a read during reorder buffer management.</entry>
</row>
<row>
<entry><literal>ReorderBufferWrite</literal></entry>
<entry>Waiting for a write during reorder buffer management.</entry>
</row>
<row>
<entry><literal>ReorderLogicalMappingRead</literal></entry>
<entry>Waiting for a read of a logical mapping during reorder buffer management.</entry>
</row>
<row>
<entry><literal>ReplicationSlotRead</literal></entry>
<entry>Waiting for a read from a replication slot control file.</entry>
</row>
<row>
<entry><literal>ReplicationSlotRestoreSync</literal></entry>
<entry>Waiting for a replication slot control file to reach stable storage while restoring it to memory.</entry>
</row>
<row>
<entry><literal>ReplicationSlotSync</literal></entry>
<entry>Waiting for a replication slot control file to reach stable storage.</entry>
</row>
<row>
<entry><literal>ReplicationSlotWrite</literal></entry>
<entry>Waiting for a write to a replication slot control file.</entry>
</row>
<row>
<entry><literal>SLRUFlushSync</literal></entry>
<entry>Waiting for SLRU data to reach stable storage during a checkpoint or database shutdown.</entry>
</row>
<row>
<entry><literal>SLRURead</literal></entry>
<entry>Waiting for a read of an SLRU page.</entry>
</row>
<row>
<entry><literal>SLRUSync</literal></entry>
<entry>Waiting for SLRU data to reach stable storage following a page write.</entry>
</row>
<row>
<entry><literal>SLRUWrite</literal></entry>
<entry>Waiting for a write of an SLRU page.</entry>
</row>
<row>
<entry><literal>SnapbuildRead</literal></entry>
<entry>Waiting for a read of a serialized historical catalog snapshot.</entry>
</row>
<row>
<entry><literal>SnapbuildSync</literal></entry>
<entry>Waiting for a serialized historical catalog snapshot to reach stable storage.</entry>
</row>
<row>
<entry><literal>SnapbuildWrite</literal></entry>
<entry>Waiting for a write of a serialized historical catalog snapshot.</entry>
</row>
<row>
<entry><literal>TimelineHistoryFileSync</literal></entry>
<entry>Waiting for a timeline history file received via streaming replication to reach stable storage.</entry>
</row>
<row>
<entry><literal>TimelineHistoryFileWrite</literal></entry>
<entry>Waiting for a write of a timeline history file received via streaming replication.</entry>
</row>
<row>
<entry><literal>TimelineHistoryRead</literal></entry>
<entry>Waiting for a read of a timeline history file.</entry>
</row>
<row>
<entry><literal>TimelineHistorySync</literal></entry>
<entry>Waiting for a newly created timeline history file to reach stable storage.</entry>
</row>
<row>
<entry><literal>TimelineHistoryWrite</literal></entry>
<entry>Waiting for a write of a newly created timeline history file.</entry>
</row>
<row>
<entry><literal>TwophaseFileRead</literal></entry>
<entry>Waiting for a read of a two phase state file.</entry>
</row>
<row>
<entry><literal>TwophaseFileSync</literal></entry>
<entry>Waiting for a two phase state file to reach stable storage.</entry>
</row>
<row>
<entry><literal>TwophaseFileWrite</literal></entry>
<entry>Waiting for a write of a two phase state file.</entry>
</row>
<row>
<entry><literal>WALBootstrapSync</literal></entry>
<entry>Waiting for WAL to reach stable storage during bootstrapping.</entry>
</row>
<row>
<entry><literal>WALBootstrapWrite</literal></entry>
<entry>Waiting for a write of a WAL page during bootstrapping.</entry>
</row>
<row>
<entry><literal>WALCopyRead</literal></entry>
<entry>Waiting for a read when creating a new WAL segment by copying an existing one.</entry>
</row>
<row>
<entry><literal>WALCopySync</literal></entry>
<entry>Waiting a new WAL segment created by copying an existing one to reach stable storage.</entry>
</row>
<row>
<entry><literal>WALCopyWrite</literal></entry>
<entry>Waiting for a write when creating a new WAL segment by copying an existing one.</entry>
</row>
<row>
<entry><literal>WALInitSync</literal></entry>
<entry>Waiting for a newly initialized WAL file to reach stable storage.</entry>
</row>
<row>
<entry><literal>WALInitWrite</literal></entry>
<entry>Waiting for a write while initializing a new WAL file.</entry>
</row>
<row>
<entry><literal>WALRead</literal></entry>
<entry>Waiting for a read from a WAL file.</entry>
</row>
<row>
<entry><literal>WALSenderTimelineHistoryRead</literal></entry>
<entry>Waiting for a read from a timeline history file during walsender timeline command.</entry>
</row>
<row>
<entry><literal>WALSync</literal></entry>
<entry>Waiting for a WAL file to reach stable storage.</entry>
</row>
<row>
<entry><literal>WALSyncMethodAssign</literal></entry>
<entry>Waiting for data to reach stable storage while assigning WAL sync method.</entry>
</row>
<row>
<entry><literal>WALWrite</literal></entry>
<entry>Waiting for a write to a WAL file.</entry>
</row>
</tbody>
</tgroup>
</table>
<note>
<para>
For tranches registered by extensions, the name is specified by extension
and this will be displayed as <structfield>wait_event</structfield>. It is quite
possible that user has registered the tranche in one of the backends (by
having allocation in dynamic shared memory) in which case other backends
won't have that information, so we display <literal>extension</literal> for such
cases.
Extensions can add <literal>LWLock</literal> types to the list shown in
<xref linkend="wait-event-lwlock-table"/>. In some cases, the name
assigned by an extension will not be available in all server processes;
so a wait event might be reported as
just <quote><literal>extension</literal></quote> rather than the
extension-assigned name.
</para>
</note>
<table id="wait-event-timeout-table">
<title>Wait Events of Type <literal>Timeout</literal></title>
<tgroup cols="2">
<thead>
<row>
<entry><literal>Timeout</literal> Wait Event</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>BaseBackupThrottle</literal></entry>
<entry>Waiting during base backup when throttling activity.</entry>
</row>
<row>
<entry><literal>PgSleep</literal></entry>
<entry>Waiting in process that called <function>pg_sleep</function>.</entry>
</row>
<row>
<entry><literal>RecoveryApplyDelay</literal></entry>
<entry>Waiting to apply WAL at recovery because it is delayed.</entry>
</row>
<row>
<entry><literal>RecoveryRetrieveRetryInterval</literal></entry>
<entry>Waiting when WAL data is not available from any kind of sources
(<filename>pg_wal</filename>, archive or stream) before trying
again to retrieve WAL data, at recovery.</entry>
</row>
<row>
<entry><literal>VacuumDelay</literal></entry>
<entry>Waiting in a cost-based vacuum delay point.</entry>
</row>
</tbody>
</tgroup>
</table>
<para>
Here is an example of how wait events can be viewed
Here is an example of how wait events can be viewed:
<programlisting>
SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event is NOT NULL;
......@@ -4497,7 +4681,8 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
</para>
<para>
Returns the wait event name if this backend is currently waiting,
otherwise NULL. See <xref linkend="wait-event-table"/> for details.
otherwise NULL. See <xref linkend="wait-event-activity-table"/> through
<xref linkend="wait-event-timeout-table"/>.
</para></entry>
</row>
......
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