Fix bugs in manipulation of PgBackendStatus.st_clienthostname.

tglsfdc · tglsfdc · commit 682c5bbec5d9 · 2014-04-01T21:30:34.000-04:00
Initialization of this field was not being done according to the st_changecount protocol (it has to be done within the changecount increment range, not outside). And the test to see if the value should be reported as null was wrong. Noted while perusing uses of Port.remote_hostname. This was wrong from the introduction of this code (commit 4a25bc1), so back-patch to 9.1.
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
@@ -2581,7 +2581,11 @@ pgstat_bestart(void)
 	beentry->st_databaseid = MyDatabaseId;
 	beentry->st_userid = userid;
 	beentry->st_clientaddr = clientaddr;
-	beentry->st_clienthostname[0] = '\0';
+	if (MyProcPort && MyProcPort->remote_hostname)
+		strlcpy(beentry->st_clienthostname, MyProcPort->remote_hostname,
+				NAMEDATALEN);
+	else
+		beentry->st_clienthostname[0] = '\0';
 	beentry->st_waiting = false;
 	beentry->st_state = STATE_UNDEFINED;
 	beentry->st_appname[0] = '\0';
@@ -2594,9 +2598,6 @@ pgstat_bestart(void)
 	beentry->st_changecount++;
 	Assert((beentry->st_changecount & 1) == 0);
 
-	if (MyProcPort && MyProcPort->remote_hostname)
-		strlcpy(beentry->st_clienthostname, MyProcPort->remote_hostname, NAMEDATALEN);
-
 	/* Update app name to current GUC setting */
 	if (application_name)
 		pgstat_report_appname(application_name);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
@@ -760,7 +760,8 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 						clean_ipv6_addr(beentry->st_clientaddr.addr.ss_family, remote_host);
 						values[11] = DirectFunctionCall1(inet_in,
 											   CStringGetDatum(remote_host));
-						if (beentry->st_clienthostname)
+						if (beentry->st_clienthostname &&
+							beentry->st_clienthostname[0])
 							values[12] = CStringGetTextDatum(beentry->st_clienthostname);
 						else
 							nulls[12] = true;
