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Back-patch checkpoint clarification docs and pg_basebackup updates
This backpatches 51e26c9 and 7220c7b, including both documentation updates clarifying the checkpoints at the beginning of base backups and the messages in verbose and progress mdoe of pg_basebackup. Author: Michael Banck Discussion: https://postgr.es/m/21444.1488142764%40sss.pgh.pa.us
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doc/src/sgml/backup.sgml

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@@ -862,7 +862,8 @@ SELECT pg_start_backup('label', false, false);
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<xref linkend="guc-checkpoint-completion-target">). This is
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usually what you want, because it minimizes the impact on query
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processing. If you want to start the backup as soon as
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possible, change the second parameter to <literal>true</>.
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possible, change the second parameter to <literal>true</>, which will
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issue an immediate checkpoint using as much I/O as available.
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</para>
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<para>

doc/src/sgml/ref/pg_basebackup.sgml

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@@ -382,7 +382,7 @@ PostgreSQL documentation
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<term><option>--checkpoint=<replaceable class="parameter">fast|spread</replaceable></option></term>
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<listitem>
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<para>
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Sets checkpoint mode to fast or spread (default) (see <xref linkend="backup-lowlevel-base-backup">).
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Sets checkpoint mode to fast (immediate) or spread (default) (see <xref linkend="backup-lowlevel-base-backup">).
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</para>
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</listitem>
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</varlistentry>
@@ -589,6 +589,14 @@ PostgreSQL documentation
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<refsect1>
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<title>Notes</title>
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<para>
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At the beginning of the backup, a checkpoint needs to be written on the
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server the backup is taken from. Especially if the option
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<literal>--checkpoint=fast</literal> is not used, this can take some time
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during which <application>pg_basebackup</application> will be appear
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to be idle.
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</para>
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<para>
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The backup will include all files in the data directory and tablespaces,
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including the configuration files and any additional files placed in the

src/bin/pg_basebackup/pg_basebackup.c

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@@ -1661,6 +1661,14 @@ BaseBackup(void)
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if (maxrate > 0)
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maxrate_clause = psprintf("MAX_RATE %u", maxrate);
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if (verbose)
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fprintf(stderr,
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_("%s: initiating base backup, waiting for checkpoint to complete\n"),
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progname);
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if (showprogress && !verbose)
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fprintf(stderr, "waiting for checkpoint\r");
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basebkp =
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psprintf("BASE_BACKUP LABEL '%s' %s %s %s %s %s %s",
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escaped_label,
@@ -1698,6 +1706,9 @@ BaseBackup(void)
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strlcpy(xlogstart, PQgetvalue(res, 0, 0), sizeof(xlogstart));
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if (verbose)
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fprintf(stderr, _("%s: checkpoint completed\n"), progname);
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/*
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* 9.3 and later sends the TLI of the starting point. With older servers,
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* assume it's the same as the latest timeline reported by

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