doc: Fix documenation for snapshot export in logical decoding.

The documentation for exported snapshots in logical decoding previously
stated that snapshot creation may fail on a hot standby. This is no longer
accurate, as snapshot exporting on standbys has been supported since
PostgreSQL 10. This commit removes the outdated description.

Additionally, the docs referred to the NOEXPORT_SNAPSHOT option to
suppress snapshot exporting in CREATE_REPLICATION_SLOT. However,
since PostgreSQL 15, NOEXPORT_SNAPSHOT is considered legacy syntax
and retained only for backward compatibility. This commit updates
the documentation for v15 and later to use the modern equivalent:
SNAPSHOT 'nothing'. The older syntax is preserved in documentation for
v14 and earlier.

Back-patched to all supported branches.

Reported-by: Kevin K Biju <kevinkbiju@gmail.com>
Author: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Kevin K Biju <kevinkbiju@gmail.com>
Discussion: https://postgr.es/m/174791480466.798.17122832105389395178@wrigleys.postgresql.org
Backpatch-through: 13

diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 38ee69dcccc7b2bcf1bcb95b47cc91f9c1886d31..a711affcad4ba414987bb5fee25ef3d3b74ef927 100644 (file)
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -354,9 +354,8 @@ postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NU
      using the slot's contents without losing any changes.
     </para>
     <para>
-     Creation of a snapshot is not always possible.  In particular, it will
-     fail when connected to a hot standby.  Applications that do not require
-     snapshot export may suppress it with the <literal>NOEXPORT_SNAPSHOT</literal>
+     Applications that do not require
+     snapshot export may suppress it with the <literal>SNAPSHOT 'nothing'</literal>
      option.
     </para>
    </sect2>