doc: Document commands that cannot be run in a transaction block

Mainly covering the new CREATE SUBSCRIPTION and DROP SUBSCRIPTION, but
ALTER DATABASE SET TABLESPACE was also missing.

3 files changed, 14 insertions, 5 deletions

diff --git a/doc/src/sgml/ref/alter_database.sgml b/doc/src/sgml/ref/alter_database.sgml
index cfc28cf9a7..9ab86127af 100644
--- a/doc/src/sgml/ref/alter_database.sgml
+++ b/doc/src/sgml/ref/alter_database.sgml
@@ -164,6 +164,10 @@ ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> RESET ALL
      <para>
       The new default tablespace of the database.
      </para>
+
+     <para>
+      This form of the command cannot be executed inside a transaction block.
+     </para>
     </listitem>
    </varlistentry>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 9f45b6f574..de505ea8d3 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -49,11 +49,6 @@ CREATE SUBSCRIPTION <replaceable class="PARAMETER">subscription_name</replaceabl
   </para>
 
   <para>
-   <command>CREATE SUBSCRIPTION</command> cannot be executed inside a
-   transaction block when the parameter <literal>create_slot</literal> is specified.
-  </para>
-
-  <para>
    Additional info about subscriptions and logical replication as a whole
    can is available at <xref linkend="logical-replication-subscription"> and
    <xref linkend="logical-replication">.
@@ -228,6 +223,11 @@ CREATE SUBSCRIPTION <replaceable class="PARAMETER">subscription_name</replaceabl
   </para>
 
   <para>
+   When creating a replication slot (the default behavior), <command>CREATE
+   SUBSCRIPTION</command> cannot be executed inside a transaction block.
+  </para>
+
+  <para>
    Creating a subscription that connects to the same database cluster (for
    example, to replicate between databases in the same cluster or to replicate
    within the same database) will only succeed if the replication slot is not
diff --git a/doc/src/sgml/ref/drop_subscription.sgml b/doc/src/sgml/ref/drop_subscription.sgml
index f535c000c4..f5734e6f30 100644
--- a/doc/src/sgml/ref/drop_subscription.sgml
+++ b/doc/src/sgml/ref/drop_subscription.sgml
@@ -93,6 +93,11 @@ DROP SUBSCRIPTION [ IF EXISTS ] <replaceable class="parameter">name</replaceable
    reserve WAL and might eventually cause the disk to fill up.  See
    also <xref linkend="logical-replication-subscription-slot">.
   </para>
+
+  <para>
+   If a subscription is associated with a replication slot, then <command>DROP
+   SUBSCRIPTION</command> cannot be executed inside a transaction block.
+  </para>
  </refsect1>
 
  <refsect1>