From fcff4bd312bd70bfa01295a7c5e4db959ae105c8 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 12 Dec 2013 12:39:57 -0500
Subject: [PATCH] Fix ancient docs/comments thinko: XID comparison is mod 2^32,
not 2^31.
Pointed out by Gianni Ciolli.
---
doc/src/sgml/maintenance.sgml | 2 +-
src/backend/access/transam/transam.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index e9b8f97ae53..3577418a162 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -401,7 +401,7 @@
as <literal>FrozenXID</>. This XID does not follow the normal XID
comparison rules and is always considered older
than every normal XID. Normal XIDs are
- compared using modulo-2<superscript>31</> arithmetic. This means
+ compared using modulo-2<superscript>32</> arithmetic. This means
that for every normal XID, there are two billion XIDs that are
<quote>older</> and two billion that are <quote>newer</>; another
way to say it is that the normal XID space is circular with no
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index a7214cf34de..833f3cd1cc7 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -304,7 +304,7 @@ TransactionIdPrecedes(TransactionId id1, TransactionId id2)
{
/*
* If either ID is a permanent XID then we can just do unsigned
- * comparison. If both are normal, do a modulo-2^31 comparison.
+ * comparison. If both are normal, do a modulo-2^32 comparison.
*/
int32 diff;
--
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