WALSender now woken up after each background flush by WALwriter, avoiding
multi-second replication delay for an all-async commit workload.
Replication delay reduced from 7s with default settings to 200ms and often
much less, allowing significantly reduced data loss at failover.
Andres Freund and Simon Riggs
END_CRIT_SECTION();
+ /*
+ * If we wrote something then we have something to send to standbys also,
+ * otherwise the replication delay become around 7s with just async commit.
+ */
+ if (wrote_something)
+ WalSndWakeup();
+
return wrote_something;
}