Allow UNLISTEN in hot-standby mode.

Since LISTEN is (still) disallowed, UNLISTEN must be a no-op in a
hot-standby session, and so there's no harm in allowing it.  This
change allows client code to not worry about whether it's connected
to a primary or standby server when performing session-state-reset
type activities.  (Note that DISCARD ALL, which includes UNLISTEN,
was already allowed, making it inconsistent to reject UNLISTEN.)

Per discussion, back-patch to all supported versions.

Shay Rojansky, reviewed by Mi Tar

Discussion: https://postgr.es/m/CADT4RqCf2gA_TJtPAjnGzkC3ZiexfBZiLmA-mV66e4UyuVv8bA@mail.gmail.com

diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 2cd06cca19751465fa27e053ac48c578f7649ec5..aab6da457f84a13b22598e89bee7511145342aac 100644 (file)
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -1686,6 +1686,11 @@ if (!triggered)
        Plugins and extensions - <command>LOAD</>
       </para>
      </listitem>
+     <listitem>
+      <para>
+       <command>UNLISTEN</command>
+      </para>
+     </listitem>
     </itemizedlist>
    </para>
 
@@ -1775,7 +1780,7 @@ if (!triggered)
      </listitem>
      <listitem>
       <para>
-       <command>LISTEN</>, <command>UNLISTEN</>, <command>NOTIFY</>
+       <command>LISTEN</>, <command>NOTIFY</>
       </para>
      </listitem>
     </itemizedlist>
@@ -1783,8 +1788,8 @@ if (!triggered)
 
    <para>
     In normal operation, <quote>read-only</> transactions are allowed to
-    use <command>LISTEN</>, <command>UNLISTEN</>, and
-    <command>NOTIFY</>, so Hot Standby sessions operate under slightly tighter
+    use <command>LISTEN</command> and <command>NOTIFY</command>,
+    so Hot Standby sessions operate under slightly tighter
     restrictions than ordinary read-only sessions.  It is possible that some
     of these restrictions might be loosened in a future release.
    </para>

diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 03cccad541bc85a6e7a7860fd08136fd169f193a..ed5bcd7a7b5fa7f15b0d6fd23bbd9c11d9413774 100644 (file)
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -621,7 +621,7 @@ standard_ProcessUtility(Node *parsetree,
                        {
                                UnlistenStmt *stmt = (UnlistenStmt *) parsetree;
 
-                               PreventCommandDuringRecovery("UNLISTEN");
+                               /* we allow UNLISTEN during recovery, as it's a noop */
                                CheckRestrictedOperation("UNLISTEN");
                                if (stmt->conditionname)
                                        Async_Unlisten(stmt->conditionname);

diff --git a/src/test/regress/expected/hs_standby_allowed.out b/src/test/regress/expected/hs_standby_allowed.out
index c26c9822f63555c2ad4bf3b9b40b8440ab271fcb..b2efb4195d9b1d3cadba9ed9ec100c7d0062b614 100644 (file)
--- a/src/test/regress/expected/hs_standby_allowed.out
+++ b/src/test/regress/expected/hs_standby_allowed.out
@@ -208,6 +208,9 @@ LOCK hs1 IN ACCESS SHARE MODE;
 LOCK hs1 IN ROW SHARE MODE;
 LOCK hs1 IN ROW EXCLUSIVE MODE;
 COMMIT;
+-- UNLISTEN
+UNLISTEN a;
+UNLISTEN *;
 -- LOAD
 -- should work, easier if there is no test for that...
 -- ALLOWED COMMANDS

diff --git a/src/test/regress/expected/hs_standby_disallowed.out b/src/test/regress/expected/hs_standby_disallowed.out
index bc117413ffdb375a0279269276581e22430ec904..dff0953e9a6987a45d669f26269d2088d9e74db9 100644 (file)
--- a/src/test/regress/expected/hs_standby_disallowed.out
+++ b/src/test/regress/expected/hs_standby_disallowed.out
@@ -118,10 +118,6 @@ listen a;
 ERROR:  cannot execute LISTEN during recovery
 notify a;
 ERROR:  cannot execute NOTIFY during recovery
-unlisten a;
-ERROR:  cannot execute UNLISTEN during recovery
-unlisten *;
-ERROR:  cannot execute UNLISTEN during recovery
 -- disallowed commands
 ANALYZE hs1;
 ERROR:  cannot execute ANALYZE during recovery

diff --git a/src/test/regress/sql/hs_standby_allowed.sql b/src/test/regress/sql/hs_standby_allowed.sql
index 7fc22148cbc986067c9d9a2d7090b62d2c72cb17..f15a1a4909281684c46d6d478e8459903709fc39 100644 (file)
--- a/src/test/regress/sql/hs_standby_allowed.sql
+++ b/src/test/regress/sql/hs_standby_allowed.sql
@@ -110,6 +110,10 @@ LOCK hs1 IN ROW SHARE MODE;
 LOCK hs1 IN ROW EXCLUSIVE MODE;
 COMMIT;
 
+-- UNLISTEN
+UNLISTEN a;
+UNLISTEN *;
+
 -- LOAD
 -- should work, easier if there is no test for that...
 

diff --git a/src/test/regress/sql/hs_standby_disallowed.sql b/src/test/regress/sql/hs_standby_disallowed.sql
index 21bbf526b741337ad05b644d6661287d8b07932e..a470600eec88330d22e9bf5b1cf7bebdbf3e9a5c 100644 (file)
--- a/src/test/regress/sql/hs_standby_disallowed.sql
+++ b/src/test/regress/sql/hs_standby_disallowed.sql
@@ -88,8 +88,6 @@ COMMIT;
 -- Listen
 listen a;
 notify a;
-unlisten a;
-unlisten *;
 
 -- disallowed commands