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doc: pg_resetwal: Add comments how the multipliers are derived 

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 2023-11-06 08:17:54 +01:00
parent 93c85db3b5
commit 6ceec8a1fe
1 changed files with 7 additions and 1 deletions
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8
doc/src/sgml/ref/pg_resetwal.sgml
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@ -166,7 +166,8 @@ PostgreSQL documentation
<command>pg_resetwal</command> is unable to determine appropriate values
by reading <filename>pg_control</filename>. Safe values can be determined as
described below. For values that take numeric arguments, hexadecimal
values can be specified by using the prefix <literal>0x</literal>.
values can be specified by using the prefix <literal>0x</literal>. Note
that these instructions only apply with the standard block size of 8 kB.
</para>
<variablelist>
@ -189,6 +190,7 @@ PostgreSQL documentation
greatest file name in the same directory. The file names are in
hexadecimal.
</para>
<!-- XXX: Should there be a multiplier, similar to the other options? -->
</listitem>
</varlistentry>
@ -272,6 +274,7 @@ PostgreSQL documentation
names are in hexadecimal, so the easiest way to do this is to specify
the option value in hexadecimal and append four zeroes.
</para>
<!-- 65536 = SLRU_PAGES_PER_SEGMENT * BLCKSZ / sizeof(MultiXactOffset) -->
</listitem>
</varlistentry>
@ -306,6 +309,7 @@ PostgreSQL documentation
The file names are in hexadecimal. There is no simple recipe such as
the ones for other options of appending zeroes.
</para>
<!-- 52352 = SLRU_PAGES_PER_SEGMENT * floor(BLCKSZ/20) * 4; see multixact.c -->
</listitem>
</varlistentry>
@ -354,6 +358,7 @@ PostgreSQL documentation
in <filename>pg_xact</filename>, <literal>-u 0x700000</literal> will work (five
trailing zeroes provide the proper multiplier).
</para>
<!-- 1048576 = SLRU_PAGES_PER_SEGMENT * BLCKSZ * CLOG_XACTS_PER_BYTE -->
</listitem>
</varlistentry>
@ -375,6 +380,7 @@ PostgreSQL documentation
in <filename>pg_xact</filename>, <literal>-x 0x1200000</literal> will work (five
trailing zeroes provide the proper multiplier).
</para>
<!-- 1048576 = SLRU_PAGES_PER_SEGMENT * BLCKSZ * CLOG_XACTS_PER_BYTE -->
</listitem>
</varlistentry>
</variablelist>