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Document age(xid) and mxid_age(xid).

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These functions have been around for some time, but commits
48b5aa3143 and 15afb7d61c were only back-patched to v16.  Let's
back-patch them to all supported versions now.

Reported-by: David Rowley <dgrowleyml@gmail.com> (commit 48b5aa3143)
Author: Bruce Momjian <bruce@momjian.us> (commit 48b5aa3143)
Co-authored-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com> (commit 15afb7d61c)
Reviewed-by: Michael Paquier <michael@paquier.xyz> (commit 15afb7d61c)
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Discussion: https://postgr.es/m/aGMCxHxLfeMdQk8m%40nathan
Backpatch-through: 13-15
This commit is contained in:
Nathan Bossart 2025-07-01 10:36:27 -05:00
parent 25cab44735
commit 326f2aaee6
1 changed files with 30 additions and 1 deletions
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31
doc/src/sgml/func.sgml
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@ -24114,6 +24114,34 @@ SELECT collation for ('foo' COLLATE "de_DE");
</thead>
<tbody>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>age</primary>
</indexterm>
<function>age</function> ( <type>xid</type> )
<returnvalue>integer</returnvalue>
</para>
<para>
Returns the number of transactions between the supplied
transaction id and the current transaction counter.
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>mxid_age</primary>
</indexterm>
<function>mxid_age</function> ( <type>xid</type> )
<returnvalue>integer</returnvalue>
</para>
<para>
Returns the number of multixacts IDs between the supplied
multixact ID and the current multixacts counter.
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
@ -24249,7 +24277,8 @@ SELECT collation for ('foo' COLLATE "de_DE");
<para>
The internal transaction ID type <type>xid</type> is 32 bits wide and
wraps around every 4 billion transactions. However,
the functions shown in <xref linkend="functions-pg-snapshot"/> use a
the functions shown in <xref linkend="functions-pg-snapshot"/>, except
<function>age</function> and <function>mxid_age</function>, use a
64-bit type <type>xid8</type> that does not wrap around during the life
of an installation, and can be converted to <type>xid</type> by casting if
required. The data type <type>pg_snapshot</type> stores information about