From 4cd54df7e27efb5dd82751fd8c7d15c475ce4a40 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddy@enterprisedb.com>
Date: Mon, 19 Apr 2021 19:25:02 +0530
Subject: [PATCH v1] Use a WaitLatch for lock waiting in lazy_truncate_heap

Instead of using pg_usleep() in lazy_truncate_heap(), use a
WaitLatch. This has the advantage that we will realize if the
postmaster has been killed since the last time we decided to
sleep.
---
 doc/src/sgml/monitoring.sgml            | 5 +++++
 src/backend/access/heap/vacuumlazy.c    | 6 +++++-
 src/backend/utils/activity/wait_event.c | 3 +++
 src/include/utils/wait_event.h          | 3 ++-
 4 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 5cf083bb77..65d51ce445 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -2249,6 +2249,11 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       <entry><literal>VacuumDelay</literal></entry>
       <entry>Waiting in a cost-based vacuum delay point.</entry>
      </row>
+     <row>
+      <entry><literal>VacuumTruncateLock</literal></entry>
+      <entry>Waiting to acquire exclusive lock on relation for truncation while
+      vacuuming.</entry>
+     </row>
     </tbody>
    </tgroup>
   </table>
diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index e90fc18aa9..dcd598fca8 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -3188,7 +3188,11 @@ lazy_truncate_heap(LVRelState *vacrel)
 				return;
 			}
 
-			pg_usleep(VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL * 1000L);
+			(void) WaitLatch(MyLatch,
+							 WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+							 VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL,
+							 WAIT_EVENT_VACUUM_TRUNCATE_LOCK);
+			ResetLatch(MyLatch);
 		}
 
 		/*
diff --git a/src/backend/utils/activity/wait_event.c b/src/backend/utils/activity/wait_event.c
index 89b5b8b7b9..694cd48315 100644
--- a/src/backend/utils/activity/wait_event.c
+++ b/src/backend/utils/activity/wait_event.c
@@ -485,6 +485,9 @@ pgstat_get_wait_timeout(WaitEventTimeout w)
 		case WAIT_EVENT_VACUUM_DELAY:
 			event_name = "VacuumDelay";
 			break;
+		case WAIT_EVENT_VACUUM_TRUNCATE_LOCK:
+			event_name = "VacuumTruncateLock";
+			break;
 			/* no default case, so that compiler will warn */
 	}
 
diff --git a/src/include/utils/wait_event.h b/src/include/utils/wait_event.h
index 47accc5ffe..60b8ca76f7 100644
--- a/src/include/utils/wait_event.h
+++ b/src/include/utils/wait_event.h
@@ -140,7 +140,8 @@ typedef enum
 	WAIT_EVENT_PG_SLEEP,
 	WAIT_EVENT_RECOVERY_APPLY_DELAY,
 	WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL,
-	WAIT_EVENT_VACUUM_DELAY
+	WAIT_EVENT_VACUUM_DELAY,
+	WAIT_EVENT_VACUUM_TRUNCATE_LOCK
 } WaitEventTimeout;
 
 /* ----------
-- 
2.25.1