Check for two_phase change at end of process_syncing_tables_for_apply.

Previously this function checked to see if we were ready to switch
to two_phase mode at its start, but that's silly: we should check
at the end, after we've done the work that might make us ready.
This simple change removes one sleep cycle from the time needed to
switch to two_phase mode.  In the real world that might not be
worth much, but it shaves a few seconds off the runtime for the
subscription test suite.

Nathan Bossart

Discussion: https://postgr.es/m/20221122004119.GA132961@nathanxps13

src/backend/replication/logical/tablesync.c

@@ -415,6 +415,7 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 	static HTAB *last_start_times = NULL;
 	ListCell   *lc;
 	bool		started_tx = false;
+	bool		should_exit = false;
 
 	Assert(!IsTransactionState());
 
@@ -446,28 +447,6 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 		last_start_times = NULL;
 	}
 
-	/*
-	 * Even when the two_phase mode is requested by the user, it remains as
-	 * 'pending' until all tablesyncs have reached READY state.
-	 *
-	 * When this happens, we restart the apply worker and (if the conditions
-	 * are still ok) then the two_phase tri-state will become 'enabled' at
-	 * that time.
-	 *
-	 * Note: If the subscription has no tables then leave the state as
-	 * PENDING, which allows ALTER SUBSCRIPTION ... REFRESH PUBLICATION to
-	 * work.
-	 */
-	if (MySubscription->twophasestate == LOGICALREP_TWOPHASE_STATE_PENDING &&
-		AllTablesyncsReady())
-	{
-		ereport(LOG,
-				(errmsg("logical replication apply worker for subscription \"%s\" will restart so that two_phase can be enabled",
-						MySubscription->name)));
-
-		proc_exit(0);
-	}
-
 	/*
 	 * Process all tables that are being synchronized.
 	 */
@@ -619,9 +598,36 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 
 	if (started_tx)
 	{
+		/*
+		 * Even when the two_phase mode is requested by the user, it remains
+		 * as 'pending' until all tablesyncs have reached READY state.
+		 *
+		 * When this happens, we restart the apply worker and (if the
+		 * conditions are still ok) then the two_phase tri-state will become
+		 * 'enabled' at that time.
+		 *
+		 * Note: If the subscription has no tables then leave the state as
+		 * PENDING, which allows ALTER SUBSCRIPTION ... REFRESH PUBLICATION to
+		 * work.
+		 */
+		if (MySubscription->twophasestate == LOGICALREP_TWOPHASE_STATE_PENDING)
+		{
+			CommandCounterIncrement();	/* make updates visible */
+			if (AllTablesyncsReady())
+			{
+				ereport(LOG,
+						(errmsg("logical replication apply worker for subscription \"%s\" will restart so that two_phase can be enabled",
+								MySubscription->name)));
+				should_exit = true;
+			}
+		}
+
 		CommitTransactionCommand();
 		pgstat_report_stat(true);
 	}
+
+	if (should_exit)
+		proc_exit(0);
 }
 
 /*
@@ -802,6 +808,7 @@ fetch_remote_table_info(char *nspname, char *relname,
 		TupleTableSlot *tslot;
 		Oid			attrsRow[] = {INT2VECTOROID};
 		StringInfoData pub_names;
+
 		initStringInfo(&pub_names);
 		foreach(lc, MySubscription->publications)
 		{