Fix varstr_cmp's special case for UTF8 encoding on Windows so that strings

that are reported as "equal" by wcscoll() are checked to see if they really
are bitwise equal, and are sorted per strcmp() if not.  We made this happen
a couple of years ago in the regular code path, but it unaccountably got
left out of the Windows/UTF8 case (probably brain fade on my part at the
time).  As in the prior set of changes, affected users may need to reindex
indexes on textual columns.

Backpatch as far as 8.2, which is the oldest release we are still supporting
on Windows.

Author: tglsfdc

src/backend/utils/adt/varlena.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.162 2008/01/01 19:45:53 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.163 2008/03/13 18:31:56 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1003,6 +1003,19 @@ varstr_cmp(char *arg1, int len1, char *arg2, int len2)
 				ereport(ERROR,
 						(errmsg("could not compare Unicode strings: %m")));
 
+			/*
+			 * In some locales wcscoll() can claim that nonidentical strings
+			 * are equal.  Believing that would be bad news for a number of
+			 * reasons, so we follow Perl's lead and sort "equal" strings
+			 * according to strcmp (on the UTF-8 representation).
+			 */
+			if (result == 0)
+			{
+				result = strncmp(arg1, arg2, Min(len1, len2));
+				if ((result == 0) && (len1 != len2))
+					result = (len1 < len2) ? -1 : 1;
+			}
+
 			if (a1p != a1buf)
 				pfree(a1p);
 			if (a2p != a2buf)