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authorPeter Eisentraut2023-11-06 07:17:54 +0000
committerPeter Eisentraut2023-11-06 08:16:00 +0000
commit6ceec8a1fe7a5028b29bbfe402f645f6fea5fb90 (patch)
treedee0752bd9a7adf33ecc9afc0d54473c3248c183
parent93c85db3b5b8d8d15b10b4c66a0e6961028470d4 (diff)
doc: pg_resetwal: Add comments how the multipliers are derived
Reviewed-by: Aleksander Alekseev <[email protected]> Discussion: https://www.postgresql.org/message-id/flat/[email protected]
-rw-r--r--doc/src/sgml/ref/pg_resetwal.sgml8
1 files changed, 7 insertions, 1 deletions
diff --git a/doc/src/sgml/ref/pg_resetwal.sgml b/doc/src/sgml/ref/pg_resetwal.sgml
index 08cd3ce5fc..cf9c7e70f2 100644
--- a/doc/src/sgml/ref/pg_resetwal.sgml
+++ b/doc/src/sgml/ref/pg_resetwal.sgml
@@ -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>