From d4116a771925379c33cf4c6634ca620ed08b551d Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Fri, 7 Apr 2017 13:41:47 -0400
Subject: [PATCH] Add ProcArrayGroupUpdate wait event.

Discussion: http://postgr.es/m/CA+TgmobgWHcXDcChX2+BqJDk2dkPVF85ZrJFhUyHHQmw8diTpA@mail.gmail.com
---
 doc/src/sgml/monitoring.sgml        | 5 ++++-
 src/backend/postmaster/pgstat.c     | 3 +++
 src/backend/storage/ipc/procarray.c | 3 +++
 src/include/pgstat.h                | 1 +
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 9856968997..b16325d390 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -1232,7 +1232,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
          <entry>Waiting in an extension.</entry>
         </row>
         <row>
-         <entry morerows="11"><literal>IPC</></entry>
+         <entry morerows="12"><literal>IPC</></entry>
          <entry><literal>BgWorkerShutdown</></entry>
          <entry>Waiting for background worker to shut down.</entry>
         </row>
@@ -1272,6 +1272,9 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
          <entry><literal>ParallelBitmapPopulate</></entry>
          <entry>Waiting for the leader to populate the TidBitmap.</entry>
         </row>
+        <row>
+         <entry><literal>ProcArrayGroupUpdate</></entry>
+         <entry>Waiting for group leader to clear transaction id at transaction end.</entry>
         <row>
          <entry><literal>SafeSnapshot</></entry>
          <entry>Waiting for a snapshot for a <literal>READ ONLY DEFERRABLE</> transaction.</entry>
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 56a8bf2d17..3fb57f060c 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3560,6 +3560,9 @@ pgstat_get_wait_ipc(WaitEventIPC w)
 		case WAIT_EVENT_PARALLEL_BITMAP_SCAN:
 			event_name = "ParallelBitmapScan";
 			break;
+		case WAIT_EVENT_PROCARRAY_GROUP_UPDATE:
+			event_name = "ProcArrayGroupUpdate";
+			break;
 		case WAIT_EVENT_SAFE_SNAPSHOT:
 			event_name = "SafeSnapshot";
 			break;
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index fb39bdc2f5..ebf6a92923 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -53,6 +53,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "storage/proc.h"
 #include "storage/procarray.h"
 #include "storage/spin.h"
@@ -513,6 +514,7 @@ ProcArrayGroupClearXid(PGPROC *proc, TransactionId latestXid)
 		int			extraWaits = 0;
 
 		/* Sleep until the leader clears our XID. */
+		pgstat_report_wait_start(WAIT_EVENT_PROCARRAY_GROUP_UPDATE);
 		for (;;)
 		{
 			/* acts as a read barrier */
@@ -521,6 +523,7 @@ ProcArrayGroupClearXid(PGPROC *proc, TransactionId latestXid)
 				break;
 			extraWaits++;
 		}
+		pgstat_report_wait_end();
 
 		Assert(pg_atomic_read_u32(&proc->procArrayGroupNext) == INVALID_PGPROCNO);
 
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index e29397f25b..5e029c0f4e 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -808,6 +808,7 @@ typedef enum
 	WAIT_EVENT_MQ_SEND,
 	WAIT_EVENT_PARALLEL_FINISH,
 	WAIT_EVENT_PARALLEL_BITMAP_SCAN,
+	WAIT_EVENT_PROCARRAY_GROUP_UPDATE,
 	WAIT_EVENT_SAFE_SNAPSHOT,
 	WAIT_EVENT_SYNC_REP,
 	WAIT_EVENT_LOGICAL_SYNC_DATA,
-- 
2.40.0