From 76e5b4c85d5d4830888044fc885b1da0d781aed0 Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Sun, 8 May 2011 23:59:31 -0400
Subject: [PATCH] Add C comment about the fact that the autovacuum limit can go
 backwards by 3, but that is it OK.

---
 src/backend/postmaster/autovacuum.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 9fa63a4e6e..fcc912f8e3 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -1108,6 +1108,7 @@ do_start_worker(void)
 	recentXid = ReadNewTransactionId();
 	xidForceLimit = recentXid - autovacuum_freeze_max_age;
 	/* ensure it's a "normal" XID, else TransactionIdPrecedes misbehaves */
+	/* this can cause the limit to go backwards by 3, but that's OK */
 	if (xidForceLimit < FirstNormalTransactionId)
 		xidForceLimit -= FirstNormalTransactionId;