Fix ancient docs/comments thinko: XID comparison is mod 2^32, not 2^31.

tglsfdc · tglsfdc · commit ccca6f56f5e0 · 2013-12-12T12:39:48.000-05:00
Pointed out by Gianni Ciolli.
diff --git 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
@@ -301,7 +301,7 @@ 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;
 

Original file line number	Diff line number	Diff line change
`@@ -301,7 +301,7 @@ TransactionIdPrecedes(TransactionId id1, TransactionId id2)`
`301`	`301`	`{`
`302`	`302`	`/*`
`303`	`303`	`* If either ID is a permanent XID then we can just do unsigned`
`304`		`- * comparison. If both are normal, do a modulo-2^31 comparison.`
	`304`	`+ * comparison. If both are normal, do a modulo-2^32 comparison.`
`305`	`305`	`*/`
`306`	`306`	`int32 diff;`
`307`	`307`