Improve logical replication worker log messages

Reduce some redundant messages to DEBUG1.  Be clearer about the
distinction between apply workers and table synchronization workers.
Add subscription and table name where possible.

Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>

src/backend/replication/logical/launcher.c

@@ -260,7 +260,7 @@ logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname, Oid userid,
 	int			nsyncworkers;
 	TimestampTz now;
 
-	ereport(LOG,
+	ereport(DEBUG1,
 	   (errmsg("starting logical replication worker for subscription \"%s\"",
 			   subname)));
 

src/backend/replication/logical/tablesync.c

@@ -133,8 +133,11 @@ finish_sync_worker(void)
 	/* Find the main apply worker and signal it. */
 	logicalrep_worker_wakeup(MyLogicalRepWorker->subid, InvalidOid);
 
+	StartTransactionCommand();
 	ereport(LOG,
-			(errmsg("logical replication synchronization worker finished processing")));
+			(errmsg("logical replication table synchronization worker for subscription \"%s\", table \"%s\" has finished",
+					MySubscription->name, get_rel_name(MyLogicalRepWorker->relid))));
+	CommitTransactionCommand();
 
 	/* Stop gracefully */
 	walrcv_disconnect(wrconn);

src/backend/replication/logical/worker.c

@@ -1325,7 +1325,7 @@ reread_subscription(void)
 	if (!newsub)
 	{
 		ereport(LOG,
-		   (errmsg("logical replication worker for subscription \"%s\" will "
+		   (errmsg("logical replication apply worker for subscription \"%s\" will "
 				   "stop because the subscription was removed",
 				   MySubscription->name)));
 
@@ -1340,7 +1340,7 @@ reread_subscription(void)
 	if (!newsub->enabled)
 	{
 		ereport(LOG,
-		   (errmsg("logical replication worker for subscription \"%s\" will "
+		   (errmsg("logical replication apply worker for subscription \"%s\" will "
 				   "stop because the subscription was disabled",
 				   MySubscription->name)));
 
@@ -1355,7 +1355,7 @@ reread_subscription(void)
 	if (strcmp(newsub->conninfo, MySubscription->conninfo) != 0)
 	{
 		ereport(LOG,
-		   (errmsg("logical replication worker for subscription \"%s\" will "
+		   (errmsg("logical replication apply worker for subscription \"%s\" will "
 				   "restart because the connection information was changed",
 				   MySubscription->name)));
 
@@ -1370,7 +1370,7 @@ reread_subscription(void)
 	if (strcmp(newsub->name, MySubscription->name) != 0)
 	{
 		ereport(LOG,
-		   (errmsg("logical replication worker for subscription \"%s\" will "
+		   (errmsg("logical replication apply worker for subscription \"%s\" will "
 				   "restart because subscription was renamed",
 				   MySubscription->name)));
 
@@ -1388,7 +1388,7 @@ reread_subscription(void)
 	if (strcmp(newsub->slotname, MySubscription->slotname) != 0)
 	{
 		ereport(LOG,
-		   (errmsg("logical replication worker for subscription \"%s\" will "
+		   (errmsg("logical replication apply worker for subscription \"%s\" will "
 				   "restart because the replication slot name was changed",
 				   MySubscription->name)));
 
@@ -1403,7 +1403,7 @@ reread_subscription(void)
 	if (!equal(newsub->publications, MySubscription->publications))
 	{
 		ereport(LOG,
-		   (errmsg("logical replication worker for subscription \"%s\" will "
+		   (errmsg("logical replication apply worker for subscription \"%s\" will "
 				   "restart because subscription's publications were changed",
 				   MySubscription->name)));
 
@@ -1503,7 +1503,7 @@ ApplyWorkerMain(Datum main_arg)
 	if (!MySubscription->enabled)
 	{
 		ereport(LOG,
-		(errmsg("logical replication worker for subscription \"%s\" will not "
+		(errmsg("logical replication apply worker for subscription \"%s\" will not "
 				"start because the subscription was disabled during startup",
 				MySubscription->name)));
 
@@ -1516,11 +1516,13 @@ ApplyWorkerMain(Datum main_arg)
 								  (Datum) 0);
 
 	if (am_tablesync_worker())
-		elog(LOG, "logical replication sync for subscription %s, table %s started",
-			 MySubscription->name, get_rel_name(MyLogicalRepWorker->relid));
+		ereport(LOG,
+				(errmsg("logical replication table synchronization worker for subscription \"%s\", table \"%s\" has started",
+						MySubscription->name, get_rel_name(MyLogicalRepWorker->relid))));
 	else
-		elog(LOG, "logical replication apply for subscription %s started",
-			 MySubscription->name);
+		ereport(LOG,
+				(errmsg("logical replication apply worker for subscription \"%s\" has started",
+						MySubscription->name)));
 
 	CommitTransactionCommand();