[CF 6239] v4 - Allow GUC settings in CREATE SUBSCRIPTION CONNECTION to take effect on publisher's walsender

This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/6239

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CAHGQGwGxSVPia+ZtJxyqWTdP_-YG_YPb=CMrZpC7fTjknARX=A@mail.gmail.com
Author(s): Fujii Masao

Author: Commitfest Bot

src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

@@ -180,17 +180,6 @@ libpqrcv_connect(const char *conninfo, bool replication, bool logical,
 			/* Tell the publisher to translate to our encoding */
 			keys[++i] = "client_encoding";
 			vals[i] = GetDatabaseEncodingName();
-
-			/*
-			 * Force assorted GUC parameters to settings that ensure that the
-			 * publisher will output data values in a form that is unambiguous
-			 * to the subscriber.  (We don't want to modify the subscriber's
-			 * GUC settings, since that might surprise user-defined code
-			 * running in the subscriber, such as triggers.)  This should
-			 * match what pg_dump does.
-			 */
-			keys[++i] = "options";
-			vals[i] = "-c datestyle=ISO -c intervalstyle=postgres -c extra_float_digits=3";
 		}
 		else
 		{
@@ -256,6 +245,38 @@ libpqrcv_connect(const char *conninfo, bool replication, bool logical,
 		PQclear(res);
 	}
 
+	/*
+	 * Force assorted GUC parameters to settings that ensure that the
+	 * publisher will output data values in a form that is unambiguous to the
+	 * subscriber.  (We don't want to modify the subscriber's GUC settings,
+	 * since that might surprise user-defined code running in the subscriber,
+	 * such as triggers.)  This should match what pg_dump does.
+	 */
+	if (replication && logical)
+	{
+		const char *params[] =
+		{"datestyle", "intervalstyle", "extra_float_digits"};
+		const char *values[] = {"ISO", "postgres", "3"};
+
+		for (int j = 0; j < lengthof(params); j++)
+		{
+			char		sql[100];
+			PGresult   *res;
+
+			sprintf(sql, "SET %s = %s", params[j], values[j]);
+			res = libpqsrv_exec(conn->streamConn, sql,
+								WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
+			if (PQresultStatus(res) != PGRES_COMMAND_OK)
+			{
+				PQclear(res);
+				*err = psprintf(_("could not set %s: %s"),
+								params[j], pchomp(PQerrorMessage(conn->streamConn)));
+				goto bad_connection;
+			}
+			PQclear(res);
+		}
+	}
+
 	conn->logical = logical;
 
 	return conn;

src/test/subscription/t/001_rep_changes.pl

@@ -438,17 +438,34 @@
 22.22|bar|2),
 	'update works with dropped subscriber column');
 
+# Verify that GUC settings supplied in the CONNECTION string take effect on
+# the publisher's walsender.  We do this by enabling log_disconnections in
+# the CONNECTION string later and checking that the publisher's log contains a
+# disconnection message.
+#
+# First, confirm that no such disconnection message appears before enabling
+# log_disconnections.
+$logfile = slurp_file($node_publisher->logfile, $log_location);
+unlike(
+	$logfile,
+	qr/disconnection: session time:/,
+	'log_disconnections has not been enabled yet');
+
 # check that change of connection string and/or publication list causes
 # restart of subscription workers. We check the state along with
 # application_name to ensure that the walsender is (re)started.
 #
 # Not all of these are registered as tests as we need to poll for a change
 # but the test suite will fail nonetheless when something goes wrong.
+#
+# Enable log_disconnections as the change of connection string,
+# which is also for the above mentioned test of GUC settings passed through
+# CONNECTION.
 my $oldpid = $node_publisher->safe_psql('postgres',
 	"SELECT pid FROM pg_stat_replication WHERE application_name = 'tap_sub' AND state = 'streaming';"
 );
 $node_subscriber->safe_psql('postgres',
-	"ALTER SUBSCRIPTION tap_sub CONNECTION '$publisher_connstr sslmode=disable'"
+	"ALTER SUBSCRIPTION tap_sub CONNECTION '$publisher_connstr options=''-c log_disconnections=on'''"
 );
 $node_publisher->poll_query_until('postgres',
 	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = 'tap_sub' AND state = 'streaming';"
@@ -552,6 +569,15 @@
   or die
   "Timed out while waiting for apply to restart after renaming SUBSCRIPTION";
 
+# Check that the expected disconnection message appears,
+# which shows that log_disconnections=on from the CONNECTION string
+# was correctly passed through to and honored by the walsender.
+$logfile = slurp_file($node_publisher->logfile, $log_location);
+like(
+	$logfile,
+	qr/disconnection: session time:/,
+	'log_disconnections in CONNECTION string had effect on publisher\'s walsender');
+
 # check all the cleanup
 $node_subscriber->safe_psql('postgres', "DROP SUBSCRIPTION tap_sub_renamed");