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.

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index 5fcce7477fb62375571590e537aa46055572bf88..327d62d7cbb5fd9f5c5a2f2af3089a8b75210dfe 100644 (file)
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -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)