Doc: add glossary term for "auxiliary process"
Add entries for existing processes not documented, too, and adjust existing definitions for consistency. Per question from Bharath Rupireddy. Author: Justin Pryzby <pryzby@telsasoft.com> Author: Alvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/CALj2ACVpYCT0M+k8zqrAa4ZQZV+ce5s6G=yajwoS1m=h-jj8NQ@mail.gmail.com
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Alvaro Herrera
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@ -48,7 +48,7 @@
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<glossterm>Analyze (operation)</glossterm>
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<glossdef>
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<para>
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The process of collecting statistics from data in
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The act of collecting statistics from data in
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<glossterm linkend="glossary-table">tables</glossterm>
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and other <glossterm linkend="glossary-relation">relations</glossterm>
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to help the <glossterm linkend="glossary-planner">query planner</glossterm>
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@ -113,8 +113,12 @@
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<para>
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A set of background processes that routinely perform
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<glossterm linkend="glossary-vacuum">vacuum</glossterm>
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and <glossterm linkend="glossary-analyze">analyze</glossterm>
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operations.
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and <glossterm linkend="glossary-analyze">analyze</glossterm> operations.
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The <glossterm linkend="glossary-auxiliary-proc">auxiliary process</glossterm>
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that coordinates the work and is always present (unless autovacuum
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is disabled) is known as the <firstterm>autovacuum launcher</firstterm>,
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and the processes that carry out the tasks are known as the
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<firstterm>autovacuum workers</firstterm>.
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</para>
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<para>
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For more information, see
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@ -123,6 +127,34 @@
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</glossdef>
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</glossentry>
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<glossentry id="glossary-auxiliary-proc">
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<glossterm>Auxiliary process</glossterm>
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<glossdef>
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<para>
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A process within an <glossterm linkend="glossary-instance">instance</glossterm>
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that is in charge of some specific background task for the instance.
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The auxiliary processes consist of <!-- in alphabetical order -->
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<!-- NB: In the code, the autovac launcher doesn't use the auxiliary
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process scaffolding; however it does behave as one so we list it
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here anyway. In addition, logger and stats collector aren't
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connected to shared memory so most code outside postmaster.c
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doesn't even consider them "procs" in the first place.
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-->
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the <glossterm linkend="glossary-autovacuum">autovacuum launcher</glossterm>
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(but not the autovacuum workers),
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the <glossterm linkend="glossary-background-writer">background writer</glossterm>,
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the <glossterm linkend="glossary-checkpointer">checkpointer</glossterm>,
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the <glossterm linkend="glossary-logger">logger</glossterm>,
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the <glossterm linkend="glossary-startup-process">startup process</glossterm>,
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the <glossterm linkend="glossary-stats-collector">statistics collector</glossterm>,
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the <glossterm linkend="glossary-wal-archiver">WAL archiver</glossterm>,
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the <glossterm linkend="glossary-wal-receiver">WAL receiver</glossterm>
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(but not the <glossterm linkend="glossary-wal-sender">WAL senders</glossterm>),
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and the <glossterm linkend="glossary-wal-writer">WAL writer</glossterm>.
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</para>
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</glossdef>
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</glossentry>
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<glossentry id="glossary-backend">
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<glossterm>Backend (process)</glossterm>
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<glossdef>
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@ -163,7 +195,8 @@
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<glossterm>Background writer (process)</glossterm>
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<glossdef>
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<para>
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A process that writes dirty
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An <glossterm linkend="glossary-auxiliary-proc">auxiliary process</glossterm>
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that writes dirty
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<glossterm linkend="glossary-data-page">data pages</glossterm> from
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<glossterm linkend="glossary-shared-memory">shared memory</glossterm> to
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the file system. It wakes up periodically, but works only for a short
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@ -285,7 +318,9 @@
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<glossterm>Checkpointer (process)</glossterm>
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<glossdef>
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<para>
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A specialized process responsible for executing checkpoints.
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An <glossterm linkend="glossary-auxiliary-proc">auxiliary process</glossterm>
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that is responsible for executing
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<glossterm linkend="glossary-checkpoint">checkpoints</glossterm>.
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</para>
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</glossdef>
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</glossentry>
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@ -778,8 +813,9 @@
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<glossterm>Instance</glossterm>
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<glossdef>
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<para>
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A group of backend and auxiliary processes that communicate using
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a common shared memory area. One
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A group of <glossterm linkend="glossary-backend">backend</glossterm> and
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<glossterm linkend="glossary-auxiliary-proc">auxiliary processes</glossterm>
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that communicate using a common shared memory area. One
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<glossterm linkend="glossary-postmaster">postmaster process</glossterm>
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manages the instance; one instance manages exactly one
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<glossterm linkend="glossary-db-cluster">database cluster</glossterm>
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@ -881,8 +917,8 @@
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<glossterm>Logger (process)</glossterm>
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<glossdef>
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<para>
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If activated, the process
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writes information about database events into the current
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An <glossterm linkend="glossary-auxiliary-proc">auxiliary process</glossterm>
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which, if enabled, writes information about database events into the current
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<glossterm linkend="glossary-log-file">log file</glossterm>.
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When reaching certain time- or
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volume-dependent criteria, a new log file is created.
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@ -1040,8 +1076,9 @@
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<glossdef>
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<para>
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The very first process of an <glossterm linkend="glossary-instance">instance</glossterm>.
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It starts and manages the other auxiliary processes and creates
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<glossterm linkend="glossary-backend">backend processes</glossterm>
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It starts and manages the
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<glossterm linkend="glossary-auxiliary-proc">auxiliary processes</glossterm>
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and creates <glossterm linkend="glossary-backend">backend processes</glossterm>
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on demand.
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</para>
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<para>
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@ -1452,6 +1489,22 @@
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</glossdef>
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</glossentry>
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<glossentry id="glossary-startup-process">
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<glossterm>Startup process</glossterm>
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<glossdef>
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<para>
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An <glossterm linkend="glossary-auxiliary-proc">auxiliary process</glossterm>
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that replays WAL during crash recovery and in a
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<glossterm linkend="glossary-replication">physical replica</glossterm>.
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</para>
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<para>
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(The name is historical: the startup process was named before
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replication was implemented; the name refers to its task as it
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relates to the server startup following a crash.)
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</para>
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</glossdef>
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</glossentry>
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<glossentry id="glossary-sql-object">
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<glossterm>SQL object</glossterm>
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<glossdef>
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@ -1514,8 +1567,10 @@
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<glossterm>Stats collector (process)</glossterm>
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<glossdef>
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<para>
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This process collects statistical information about the
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<glossterm linkend="glossary-instance">instance</glossterm>'s activities.
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An <glossterm linkend="glossary-auxiliary-proc">auxiliary process</glossterm>
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which, if enabled, receives statistical information
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about the <glossterm linkend="glossary-instance">instance</glossterm>'s
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activities.
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</para>
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<para>
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For more information, see
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@ -1856,7 +1911,9 @@
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<glossterm>WAL archiver (process)</glossterm>
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<glossdef>
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<para>
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A process that saves copies of <glossterm linkend="glossary-wal-file">WAL files</glossterm>
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An <glossterm linkend="glossary-auxiliary-proc">auxiliary process</glossterm>
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which, if enabled, saves copies of
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<glossterm linkend="glossary-wal-file">WAL files</glossterm>
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for the purpose of creating backups or keeping
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<glossterm linkend="glossary-replica">replicas</glossterm> current.
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</para>
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@ -1914,11 +1971,44 @@
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</glossdef>
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</glossentry>
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<glossentry id="glossary-wal-receiver">
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<glossterm>WAL receiver</glossterm>
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<glossdef>
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<para>
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An <glossterm linkend="glossary-auxiliary-proc">auxiliary process</glossterm>
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that runs on a <glossterm linkend="glossary-replica">replica</glossterm>
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to receive WAL from the
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<glossterm linkend="glossary-primary-server">primary server</glossterm>
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for replay by the
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<glossterm linkend="glossary-startup-process">startup process</glossterm>.
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</para>
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<para>
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For more information, see
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<xref linkend="warm-standby"/>.
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</para>
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</glossdef>
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</glossentry>
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<glossentry>
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<glossterm>WAL segment</glossterm>
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<glosssee otherterm="glossary-wal-file" />
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</glossentry>
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<glossentry id="glossary-wal-sender">
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<glossterm>WAL sender (process)</glossterm>
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<glossdef>
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<para>
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A special <glossterm linkend="glossary-backend">backend process</glossterm>
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that streams WAL over a network. The receiving end can be a
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<glossterm linkend="glossary-wal-receiver">WAL receiver</glossterm>
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in a <glossterm linkend="glossary-replica">replica</glossterm>,
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<xref linkend="app-pgreceivewal"/>, or any other client program
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that speaks the replication protocol.
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</para>
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</glossdef>
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</glossentry>
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<glossentry id="glossary-wal-writer">
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<glossterm>WAL writer (process)</glossterm>
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<glossdef>
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@ -422,6 +422,8 @@ extern ProcessingMode Mode;
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* Auxiliary-process type identifiers. These used to be in bootstrap.h
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* but it seems saner to have them here, with the ProcessingMode stuff.
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* The MyAuxProcType global is defined and set in auxprocess.c.
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*
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* Make sure to list in the glossary any items you add here.
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*/
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typedef enum
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