Update comments in multixact.c

From cfb627fbe57c37667265be1cae161c2e507314a3 Mon Sep 17 00:00:00 2001
From: Shi Yu <shiy.fnst@fujitsu.com>
Date: Wed, 18 Jan 2023 10:08:23 +0800
Subject: [PATCH v1] Update comments in multixact.c

Update some comments in multixact.c because SLRU truncation for multixacts is
performed during VACUUM, instead of checkpoint.
---
 src/backend/access/transam/multixact.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index e75e1fdf74..ec98885f97 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -261,7 +261,7 @@ typedef struct MultiXactStateData
 	 * we compute it (using nextMXact if none are valid).  Each backend is
 	 * required not to attempt to access any SLRU data for MultiXactIds older
 	 * than its own OldestVisibleMXactId[] setting; this is necessary because
-	 * the checkpointer could truncate away such data at any instant.
+	 * the VACUUM could truncate away such data at any instant.
 	 *
 	 * The oldest valid value among all of the OldestMemberMXactId[] and
 	 * OldestVisibleMXactId[] entries is considered by vacuum as the earliest
@@ -669,7 +669,7 @@ MultiXactIdSetOldestMember(void)
  *
  * We set the OldestVisibleMXactId for a given transaction the first time
  * it's going to inspect any MultiXactId.  Once we have set this, we are
- * guaranteed that the checkpointer won't truncate off SLRU data for
+ * guaranteed that the VACUUM won't truncate off SLRU data for
  * MultiXactIds at or after our OldestVisibleMXactId.
  *
  * The value to set is the oldest of nextMXact and all the valid per-backend
-- 
2.31.1