Allow ICU to use SortSupport on Windows with UTF-8

There is no reason to ever prevent the use of SortSupport on Windows
when ICU locales are used.  We previously avoided SortSupport on Windows
with UTF-8 server encoding and a non C-locale due to restrictions in
Windows' libc functionality.

This is now considered to be a restriction in one platform's libc
collation provider, and not a more general platform restriction.

Reported-by: Peter Geoghegan <pg@bowt.ie>

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index 260efd519aac733b58d8ecf43bac1605895869da..4b5483dbb97e35289fc6ac6ae8856bcae1b0b80b 100644 (file)
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -1823,12 +1823,6 @@ varstr_sortsupport(SortSupport ssup, Oid collid, bool bpchar)
         * requirements of BpChar callers.  However, if LC_COLLATE = C, we can
         * make things quite a bit faster with varstrfastcmp_c or bpcharfastcmp_c,
         * both of which use memcmp() rather than strcoll().
-        *
-        * There is a further exception on Windows.  When the database encoding is
-        * UTF-8 and we are not using the C collation, complex hacks are required.
-        * We don't currently have a comparator that handles that case, so we fall
-        * back on the slow method of having the sort code invoke bttextcmp() (in
-        * the case of text) via the fmgr trampoline.
         */
        if (lc_collate_is_c(collid))
        {
@@ -1839,14 +1833,8 @@ varstr_sortsupport(SortSupport ssup, Oid collid, bool bpchar)
 
                collate_c = true;
        }
-#ifdef WIN32
-       else if (GetDatabaseEncoding() == PG_UTF8)
-               return;
-#endif
        else
        {
-               ssup->comparator = varstrfastcmp_locale;
-
                /*
                 * We need a collation-sensitive comparison.  To make things faster,
                 * we'll figure out the collation based on the locale id and cache the
@@ -1867,6 +1855,22 @@ varstr_sortsupport(SortSupport ssup, Oid collid, bool bpchar)
                        }
                        locale = pg_newlocale_from_collation(collid);
                }
+
+               /*
+                * There is a further exception on Windows.  When the database
+                * encoding is UTF-8 and we are not using the C collation, complex
+                * hacks are required.  We don't currently have a comparator that
+                * handles that case, so we fall back on the slow method of having the
+                * sort code invoke bttextcmp() (in the case of text) via the fmgr
+                * trampoline.  ICU locales work just the same on Windows, however.
+                */
+#ifdef WIN32
+               if (GetDatabaseEncoding() == PG_UTF8 &&
+                       !(locale && locale->provider == COLLPROVIDER_ICU))
+                       return;
+#endif
+
+               ssup->comparator = varstrfastcmp_locale;
        }
 
        /*