From e83bee8ddcc75881002efb69a293b2b9d1d2be78 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 1 Apr 2014 21:30:14 -0400
Subject: [PATCH] Fix bugs in manipulation of
 PgBackendStatus.st_clienthostname.

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 4a25bc145),
so back-patch to 9.1.
---
 src/backend/postmaster/pgstat.c     | 9 +++++----
 src/backend/utils/adt/pgstatfuncs.c | 3 ++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index edad1401e45..214d1849a13 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -2458,7 +2458,11 @@ 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';
@@ -2471,9 +2475,6 @@ 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
index 97a4754e924..4d3f62e508d 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -723,7 +723,8 @@ 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;
-- 
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