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doc: Improve documentation about pg_resetwal -f option 

Reviewed-by: Aleksander Alekseev <aleksander@timescale.com>
Discussion: https://www.postgresql.org/message-id/flat/0f3ab4a1-ae80-56e8-3426-6b4a02507687@eisentraut.org
This commit is contained in:
Peter Eisentraut 2023-09-28 12:08:54 +02:00
parent a11d8e10f2
commit 5f1b00e64a
2 changed files with 53 additions and 12 deletions
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62
doc/src/sgml/ref/pg_resetwal.sgml
View File

@ -52,21 +52,33 @@ PostgreSQL documentation
</para>
<para>
After running this command, it should be possible to start the server,
Some options, such as <option>--wal-segsize</option> (see below), can also
be used to modify certain global settings of a database cluster without the
need to rerun <command>initdb</command>. This can be done safely on an
otherwise sound database cluster, if none of the dangerous modes mentioned
below are used.
</para>
<para>
If <command>pg_resetwal</command> is used on a data directory where the
server has been cleanly shut down and the control file is sound, then it
will have no effect on the contents of the database system, except that no
longer used WAL files are cleared away. Any other use is potentially
dangerous and must be done with great care. <command>pg_resetwal</command>
will require the <option>-f</option> (force) option to be specified before
working on a data directory in an unclean shutdown state or with a
corrupted control file.
</para>
<para>
After running this command on a data directory with corrupted WAL or a
corrupted control file, it should be possible to start the server,
but bear in mind that the database might contain inconsistent data due to
partially-committed transactions. You should immediately dump your data,
run <command>initdb</command>, and restore. After restore, check for
inconsistencies and repair as needed.
</para>
<para>
This utility can only be run by the user who installed the server, because
it requires read/write access to the data directory.
For safety reasons, you must specify the data directory on the command line.
<command>pg_resetwal</command> does not use the environment variable
<envar>PGDATA</envar>.
</para>
<para>
If <command>pg_resetwal</command> complains that it cannot determine
valid data for <filename>pg_control</filename>, you can force it to proceed anyway
@ -82,19 +94,41 @@ PostgreSQL documentation
execute any data-modifying operations in the database before you dump,
as any such action is likely to make the corruption worse.
</para>
<para>
This utility can only be run by the user who installed the server, because
it requires read/write access to the data directory.
</para>
</refsect1>
<refsect1>
<title>Options</title>
<variablelist>
<varlistentry>
<term><replaceable class="parameter">datadir</replaceable></term>
<term><option>-D <replaceable class="parameter">datadir</replaceable></option></term>
<term><option>--pgdata=<replaceable class="parameter">datadir</replaceable></option></term>
<listitem>
<para>
Specifies the location of the database directory.
For safety reasons, you must specify the data directory on the command
line. <command>pg_resetwal</command> does not use the environment
variable <envar>PGDATA</envar>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-f</option></term>
<term><option>--force</option></term>
<listitem>
<para>
Force <command>pg_resetwal</command> to proceed even if it cannot determine
valid data for <filename>pg_control</filename>, as explained above.
Force <command>pg_resetwal</command> to proceed even in situations where
it could be dangerous, as explained above. Specifically, this option is
required to proceed if the server had not been cleanly shut down or if
<command>pg_resetwal</command> cannot determine valid data for
<filename>pg_control</filename>.
</para>
</listitem>
</varlistentry>
@ -284,6 +318,12 @@ PostgreSQL documentation
linkend="app-initdb"/> for more information.
</para>
<para>
This option can also be used to change the WAL segment size of an
existing database cluster, avoiding the need to
re-<command>initdb</command>.
</para>
<note>
<para>
While <command>pg_resetwal</command> will set the WAL starting address

3
src/bin/pg_resetwal/pg_resetwal.c
View File

@ -1135,7 +1135,8 @@ usage(void)
printf(_("\nOptions:\n"));
printf(_(" [-D, --pgdata=]DATADIR data directory\n"));
printf(_(" -f, --force force update to be done\n"));
printf(_(" -f, --force force update to be done even after unclean shutdown or\n"
" if pg_control values had to be guessed\n"));
printf(_(" -n, --dry-run no update, just show what would be done\n"));
printf(_(" -V, --version output version information, then exit\n"));
printf(_(" -?, --help show this help, then exit\n"));